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Sex Differentiation (sex + differentiation)
Kinds of Sex Differentiation Selected AbstractsEpigenetic abnormality of SRY gene in the adult XY female with pericentric inversion of the Y chromosomeCONGENITAL ANOMALIES, Issue 2 2010Tomoko Mitsuhashi ABSTRACT In normal ontogenetic development, the expression of the sex-determining region of the Y chromosome (SRY) gene, involved in the first step of male sex differentiation, is spatiotemporally regulated in an elaborate fashion. SRY is expressed in germ cells and Sertoli cells in adult testes. However, only few reports have focused on the expressions of SRY and the other sex-determining genes in both the classical organ developing through these genes (gonad) and the peripheral tissue (skin) of adult XY females. In this study, we examined the gonadal tissue and fibroblasts of a 17-year-old woman suspected of having disorders of sexual differentiation by cytogenetic, histological, and molecular analyses. The patient was found to have the 46,X,inv(Y)(p11.2q11.2) karyotype and streak gonads with abnormally prolonged SRY expression. The sex-determining gene expressions in the patient-derived fibroblasts were significantly changed relative to those from a normal male. Further, the acetylated histone H3 levels in the SRY region were significantly high relative to those of the normal male. As SRY is epistatic in the sex-determination pathway, the prolonged SRY expression possibly induced a destabilizing effect on the expressions of the downstream sex-determining genes. Collectively, alterations in the sex-determining gene expressions persisted in association with disorders of sexual differentiation not only in the streak gonads but also in the skin of the patient. The findings suggest that correct regulation of SRY expression is crucial for normal male sex differentiation, even if SRY is translated normally. [source] Expression of AMH, SF1, and SOX9 in gonads of genetic female chickens during sex reversal induced by an aromatase inhibitorDEVELOPMENTAL DYNAMICS, Issue 2 2001Séverine Vaillant Abstract Aromatase inhibitors administered prior to histological signs of gonadal sex differentiation can induce sex reversal of genetic female chickens. Under the effects of Fadrozole (CGS 16949A), a nonsteroidal aromatase inhibitor, the right gonad generally becomes a testis, and the left gonad a testis or an ovotestis. We have compared the expression pattern of the genes encoding AMH (the anti-Müllerian hormone), SF1 (steroidogenic factor 1), and SOX9 (a transcription factor related to SRY) in these sex-reversed gonads with that in control testes and ovaries, using in situ hybridization with riboprobes on gonadal sections. In control males, the three genes are expressed in Sertoli cells of testicular cords; however, only SOX9 is male specific, since as observed previously AMH and SF1 but not SOX9 are expressed in the control female gonads. In addition to testicular-like cords, sex-reversed gonads present many lacunae with a composite, thick and flat epithelium. We show that during embryonic and postnatal development, AMH, SF1 and SOX9 are expressed in the epithelium of testicular-like cords and in the thickened part but not in the flattened part of the epithelium of composite lacunae. AMH and SF1 but not SOX9 are expressed in follicular cells of ovotestes. Coexpression of the three genes, of which SOX9 is a specific Sertoli-cell marker, provides strong evidence for the transdifferentiation of ovarian into testicular epithelium in gonads of female chickens treated with Fadrozole. © 2001 Wiley-Liss, Inc. [source] Age-dependent differential expression of genes involved in steroid signalling pathway in the brain of protandrous black porgy, Acanthopagrus schlegeliDEVELOPMENTAL NEUROBIOLOGY, Issue 5 2009Sherly Tomy Abstract The mechanisms underlying brain sex differentiation in animals are poorly understood. In the present study, using black porgy, Acanthopagrus schlegeli, as primary experimental model, we investigated the temporal expression patterns of receptors for androgen (ar) and estrogen (esr1 and esr2a) in the brain during posthatching ages and analyzed them against the timing of gonadal germ cell development. We hypothesized that endogenous estrogens naturally masculinize the brain of black porgy. The expression of sex steroid receptors was studied in relation to a wider suite of other related genes (nr5a2, nr0b1, star, and cyp19a1b) to provide some insight into the monomale sex differentiation pattern observed in this species. Our results revealed a highly significant increase in esr1 together with the increase in esr2a at 120 dph (days posthatching), suggesting a significant role for esr in sex differentiation in this species. Temporal expression patterns of nr5a2, nr0b1, star, sex steroid receptors, and cyp19a1b in the brain provided evidence for their physiological roles in the monomale sex differentiation in this species. The expression of nr5a2, star, ar, esr1, esr2a, and cyp19a1b increased at 120 dph, a period when brain sex differentiation probably occurs in this species. The study also suggests that neurosteroidogenesis in black porgy may be regulated by both nr5a2 -dependent and nr5a2 -independent mechanisms. The results demonstrated striking differences in the abundance of the gene transcripts in discrete brain region throughout ontogeny. In addition, the sex steroid hormone levels and aromatase activity in brain at different developmental states and the changes in the gene expression patterns in response to aromatase inhibitor treatment are also discussed. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] Effects of 4-nonylphenol and 4- tert -octylphenol on sex differentiation and vitellogenin induction in medaka (Oryzias latipes)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 7 2003Masanori Seki Abstract Medaka (Oryzias latipes) were continuously exposed to various concentrations of two alkylphenols, 4-nonylphenol (NP) and 4- tert -octylphenol (OP), from fertilized eggs to 60 d posthatch. The effects on sexual differentiation and hepatic vitellogenin (VTG) induction in medaka were assessed to elucidate the lowest-observed-effect concentrations (LOECs) of NP and OP for these events during early life stages. The LOECs of NP and OP for these events were 11.6 and 11.4 ,g/L, respectively. These results suggest that NP and OP may have adverse effects at similar concentrations during early life stage in medaka. Additionally, we investigated whether the abnormal sex differentiation induced by these alkylphenols would be permanent or reversible once the medaka were returned to clean water. The appearance of the secondary sex characteristics reverted from female to male when fish were returned to clean water. However, gonadal histology showed that intersex gonads still existed, even after the fish were transferred to clean water for two months. These results suggest that the induced feminization of secondary sex characteristics in medaka exposed to alkylphenols during the stage of sexual differentiation may not always be permanent, but the gonadal alteration (testisova) may continue much longer. [source] Gonadogenesis in early developmental stages of Acipenser naccarii and influence of estrogen immersion on feminizationJOURNAL OF APPLIED ICHTHYOLOGY, Issue 1 2007G. Grandi Summary Gonad development processes and the effects of a single 8-hour immersion treatment with 17, -estradiol (E2, 400 ,g L,1) on sex differentation in the Adriatic sturgeon, Acipenser naccarii, were investigated. After migration of germ cells, gonadal ridges appeared in 16- to 18-day old larvae and undifferentiated gonads in 55- to 60-day old larvae. Putative ovaries with notches in the germinal epithelium and presumed testes with smooth germinal epithelium appeared in 180,185-day old juveniles. Ovaries with proliferating oogonia and early meiotic oocytes clusters were observed in 292-day old juveniles. Testes did not exhibit germ cell mitosis until 430 days of age. Developmental stages in E2 -treated animals closely followed those of controls up to 430 days. The treatment significantly increased the percentage of ovaries when administered to embryos about 1.5 day before hatching, while did not significantly altered the normal 1/1 sex ratio when administered to 1.5-day old pre-larvae and 10-day old larvae. It is likely that in A. naccarii exogenous E2 administration may act through a feedback mechanism of self-supporting steroid production and that steroids are the physiological inducers of sex differentiation, as in most teleosts. The E2 -immersion treatment, easier than time-consuming administration through food, could be a good approach to control sex differentiation and caviar production. [source] Morphological ontogeny of the gonad of three plectropomid species through sex differentiation and transitionJOURNAL OF FISH BIOLOGY, Issue 1 2003S. Adams The gonadal ontogeny through sex differentiation and transition of three protogynous coral trout species, Plectropomus leopardus, P. maculatus and P. laevis was described, based on anatomical and germinal differences along the length of the reproductive tract. Gonads of immature and mature females, sex changing individuals (transitionals) and males were examined. Specific anatomical features that were compared between sexual phases included the presence and structure of sperm sinuses, gonadal musculature and germinal cell types. All three coral trout species first differentiated as an immature female. The sexual pattern of P. leopardus and P. maculatus was concluded to be diandric protogynous hermaphroditism (males were derived from the juvenile phase as well as through sex change of mature females). Plectropomus laevis was found to be monandric as males were only derived through sex change in mature females. Structural changes did not occur concomitantly with the germinal changes associated with sex change in these Plectropomus species, which is atypical for protogynous species described to date. Precursory sperm sinuses in the dorso-medial region of the gonad were present, although non-functional, in a proportion of immature and mature females of all three species. These proportions, however, varied between species depending on the sexual pattern. The structural and germinal changes observed were hypothesized as anatomical adaptations that aid in minimizing time spent in the (non-reproductive) sexual transition phase and maximizing flexibility in male development in the diandric species. [source] Gonadal morphogenesis and sex differentiation in intraovarian embryos of the viviparous fish Zoarces viviparus (Teleostei, Perciformes, Zoarcidae): A histological and ultrastructural studyJOURNAL OF MORPHOLOGY, Issue 9 2006Tina H. Rasmussen Abstract It is essential to know the timing and process of normal gonadal differentiation and development in the specific species being investigated in order to evaluate the effect of exposure to endocrine-disrupting chemicals on these processes. In the present study gonadal sex differentiation and development were investigated in embryos of a viviparous species of marine fish, the eelpout, Zoarces viviparus, during their intraovarian development (early September to January) using light and electron microscopy. In both sexes of the embryos at the time of hatching (September 20) the initially undifferentiated paired bilobed gonad contains primordial germ cells. In the female embryos, ovarian differentiation, initiated 14 days posthatch (dph), is characterized by the initial formation of the endoovarian cavity of the single ovary as well as by the presence of some early meiotic oocytes in a chromatin-nucleolus stage. By 30 dph, the endoovarian cavity has formed. By 44 dph and onward, the ovary and the oocytes grow in size and at 134 dph, just prior to birth, the majority of the oocytes are at the perinucleolar stage of primary growth and definitive follicles have formed. In the presumptive bilobed testis of the male embryos, the germ cells (spermatogonia), in contrast to the germ cells of the ovary, remain quiescent and do not enter meiosis during intraovarian development. However, other structural (somatic) changes, such as the initial formation of the sperm duct (30 dph), the presence of blood vessels in the stromal areas of the testis (30 dph), and the appearance of developing testicular lobules (102 dph), indicate testicular differentiation. Ultrastructually, the features of the primordial germ cells, oogonia, and spermatogonia are similar, including nuage, mitochondria, endoplasmic reticulum, and Golgi complexes. J. Morphol. © 2006 Wiley-Liss, Inc. [source] Temperature Influences the Ontogenetic Expression of Aromatase and Oestrogen Receptor mRNA in the Developing Tilapia (Oreochromis mossambicus) BrainJOURNAL OF NEUROENDOCRINOLOGY, Issue 1 2003C. -L. Abstract Water temperature has a differential influence on the development of central neurotransmitter systems according to the developmental period in tilapia (Oreochromis mossambicus). Aromatase and oestrogen receptors (ERs) represent important components of the mechanism of brain differentiation. Gene expression of aromatase and ERs is modulated by neurotransmitters in the developing brain. In the present study, the quantitative reverse transcription-polymerase chain reaction method was used to investigate the effects of temperature on the ontogenetic expression of aromatase and ERs in the developing tilapia brain. Before day 10 posthatching, exposure to a higher temperature (32 °C) resulted in a significant increase in the expression of brain aromatase; conversely, a lower temperature (20 °C) resulted in a decrease. ER, expression was depressed in accordance with the decrease of temperature, but ER, was unaffected by temperature. Between days 10 and 20, neither brain aromatase nor ER, expression was altered by temperature, whereas ER, expression was significantly enhanced by exposure to 32 °C. Between days 20 and 30, brain aromatase significantly increased at the higher temperature and decreased at 20 °C, but neither ER, nor ER, was affected by temperature. The expression of both brain aromatase and ERs, differentially regulated according to the temperature and to the developmental period, could be related to brain,sex differentiation. [source] Molecular cloning and expression analysis of Fshr and Lhr in relation to Fshb and Lhb subunits during the period of temperature-dependent sex determination in pejerrey Odontesthes bonariensisMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 6 2010Takahiro Shinoda In this study, we cloned and characterized the follicle stimulating hormone receptor (Fshr) and luteinizing hormone receptor (Lhr) cDNAs of pejerrey Odontesthes bonariensis, a species with temperature-dependent sex determination (TSD), and analyzed their expression in relation to Fshb and Lhb subunits during gonadogenesis at temperatures producing only females (17°C, FPT), both sexes (25°C, MixPT), and only males (29°C, MPT). The pejerrey Fshr cDNA had 3,069,bp for a mature protein of 694 amino acids (aa) and a signal peptide of 22 aa; the Lhr cDNA had 2,936,bp for a mature protein of 676 aa and a signal peptide of 25 aa. With the exception of Lhr in fish at the MPT, all genes showed significant increases and/or peaks of expression before histological differentiation of the gonads regardless of temperature. Larvae at the FPT had lower Fshb and Lhb but higher Lhr expression during the TSD period than those at the MPT; a clear pattern could not be ascertained for Fshr. At the MixPT, Fshb, Lhb, and Lhr mRNA increased in approximately half of the fish during TSD and sex differentiation and the sex ratio was 55.2% male. Based on the above results, it is suggested that animals with high Fshb and Lhb and low Lhr values represent putative males. These evidences, together with other studies, suggest that temperature may signal through the pituitary (differential expression of Fshb and Lhb) down to the gonads (differential expression of Lhr), probably affecting the regulation of steroidogenesis during the TSD process of pejerrey. Mol. Reprod. Dev. 77: 521,532, 2010. © 2010 Wiley-Liss, Inc. [source] Temperature effects on sex determination and ontogenetic gene expression of the aromatases cyp19a and cyp19b, and the estrogen receptors esr1 and esr2 in atlantic halibut (Hippoglossus hippoglossus)MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 12 2006Solveig van Nes Abstract The aromatase (CYP19) and estrogen receptor (ESR) play important roles in the molecular mechanism of sex determination and differentiation of lower vertebrates. Several studies have proven these mechanisms to be temperature sensitive, which can influence the direction of phenotypic gender development. A temperature study was conducted to examine the effect of temperature on the sex differentiation in farmed Atlantic halibut. Sexually undifferentiated larvae were exposed to 7°C, 10°C, or 13°C during gonadal differentiation. Temperature effects on the transcription rate of the aromatase genes cyp19a (ovary type) and cyp19b (brain type) and the ESR genes esr1 and esr2 were examined by quantitative real-time PCR. With increasing temperatures, both cyp19a mRNA levels and the female incidence showed a decreasing trend, thus strongly indicating a relation between the expression of cyp19a and morphological ovary differentiation. In contrast to cyp19a, the levels of cyp19b, esr1, and esr2 mRNA strongly increased in all temperature groups throughout the study period, and did not show obvious temperature-related expression patterns. The present data provide evidence that posthatching temperature exposure significantly affects the expression of cyp19a mRNA during the developmental period and that high temperature possibly influences genetic sex determination in Atlantic halibut. Though, the female incidence never exceeded 50%, suggesting that only the homogametic (XX) female is thermolabile. So whereas temperature treatment is not likely suitable for direct feminization in halibut, the possibility for high-temperature production of XX neomales for broodstock to obtain all-female offspring by crossing with XX females is suggested. Mol. Reprod. Dev. 73: 1481,1490, 2006. © 2006 Wiley-Liss, Inc. [source] Stage-specific regulatory element of mouse Sry gene,MOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2003Kou Yokouchi Abstract Sry expression is essential for initiating male sex differentiation, and the expression occurs only during a restricted period in the developing gonad. It is thought that Sry is part of a pathway of genes that regulate sex determination. Although the interactions of several genes with Sry expression have been suggested, the exact cascade of gene expression regulating Sry transcription is entirely obscure because there is no available cell line expressing Sry and reflecting an in vivo condition. The present study was carried out to investigate the cis -acting element of the mouse Sry that responds stage specifically to its expression, in part, using transgenic mice expressing GFP on the Y chromosome. Ten DNA fragments were generated by digesting the 5, upstream region (positions 5491,8039; 2,549 bp) of mouse Sry with appropriate restriction enzymes. In an electrophoretic mobility assay with these fragments, the region from position 5491 to position 5799 (309 bp) was identified as forming specific protein,DNA complexes with nuclear extracts from 11.5 days post coitus (dpc) gonads, but not from 12.5 and 13.5-dpc gonads. This region also formed specific protein,DNA complexes with the nuclear extracts from adult testicular germ cells that generate only a circular form from Sry. This stage-specific responsive region was narrowed down to positions 5559,5616 by DNase I footprinting analysis. The assay of DNase I hypersensitive (HS) using the nuclear lysates from the 11.5-dpc urogenital ridges demonstrated that the novel HS site was located in the proximity of position 5600. This region DNase I HS was also detected at the same position when the lysates from adult testicular germ cells were applied. The results indicate that the present HS site may be involved in the transcriptional regulation of the linear and/or circular molecule transcripts from mouse Sry gene. Mol. Reprod. Dev. 64: 389,396, 2003. © 2003 Wiley-Liss, Inc. [source] Androgen receptor corepressors: An overviewTHE PROSTATE, Issue 2 2005Liang Wang Androgens play pivotal roles in sex differentiation and development, in reproductive functions, and sexual behavior. The actions of androgens are mediated through the intracellular androgen receptor (AR), a member of the nuclear receptor (NR) superfamily, which regulates a wide range of target gene expression. Recent studies indicate that the proper transcriptional activity of AR is modulated by AR coregulators, including coactivators that can enhance AR transactivation and corepressors that can suppress AR transactivation. Here, we summarize the recent discoveries relating to AR corepressor function with the following different mechanisms: (1) corepressors that inhibit the DNA binding or nuclear translocation of AR; (2) corepressors that recruit histone deacetylases; (3) corepressors that interrupt the interaction between AR and its coactivators; (4) corepressors that interrupt the interaction between the N-terminus and C-terminus of AR; (5) corepressors that function as scaffolds for other AR coregulators; (6) corepressors that target the basal transcriptional machinery; (7) other mechanisms. The potential impact and future directions of AR corepressors are also discussed. © 2004 Wiley-Liss, Inc. [source] Establishment of a strain inheriting a sex-linked SNP marker in Patagonian pejerrey (Odontesthes hatcheri), a species with both genotypic and temperature-dependent sex determinationANIMAL GENETICS, Issue 1 2010R. S. Hattori Summary The Patagonian pejerrey Odontesthes hatcheri is an atherinopsid species presenting genotypic sex determination (GSD) at intermediate temperatures and temperature-dependent sex determination at the low and high ranges of thermal tolerance. A recent study revealed the presence of a sex-linked SNP marker in some males of this species, but a strain which inherits the marker faithfully has not been established. This research was conducted to develop such a strain, for use as a tool to study the molecular mechanisms of gonadal sex differentiation and sexual dimorphism, and to obtain basic information on the GSD mode in this species. For these purposes, we performed backcrosses and full-sibling crosses using males and females whose presumptive genotypic sex was inferred from the presence of the sex-linked SNP marker. Four backcrosses between SNP, daughters and their SNP+ father generated balanced sex ratios with the phenotypic sex matching the genotypic sex in most cases (98.21%) at an intermediate, sexually neutral temperature (21 °C). Full-sibling crosses between these four SNP, females and their SNP+ brothers produced three progenies with balanced sex ratios and one with 94.4% males. The results of this study confirm that a strain inheriting the sex-linked SNP marker was successfully developed. Moreover, the inheritance pattern of the marker and the sex ratios of the progenies provide strong evidence that the GSD mode in O. hatcheri is the XX,XY system. [source] Effects of a nonsteroidal aromatase inhibitor on gonadal differentiation of bluegill sunfish Lepomis macrochirusAQUACULTURE RESEARCH, Issue 9 2010Ze-Xia Gao Abstract In the present study, the efficacy of Letrozole, a potent nonsteroidal aromatase inhibitor (AI), on gonadal sex differentiation and sex reversal was examined in bluegill sunfish (Lepomis macrochirus). In Experiment 1, using AI diet treatments (50, 150, 250 and 500 mg kg,1) from 30 to 90 days posthatch (dph), AI interrupted ovarian cavity formation at a dose of 500 mg kg1 diet and one intersex fish was identified in this group. The proportions of males in all the treated groups were significantly higher than those in the control group. In Experiment 2, using AI immersion treatments (250, 500 and 1000 ,g L,1) during 30,50 dph, the treated groups of 500 and 1000 ,g L,1 produced significantly more males than the control and 250 ,g L,1 groups. Histological examination revealed no differences in ovary or testis tissue between control and AI-treated fish. There were no significant differences detected in body weight and length among the AI treated and control groups (P>0.05) for both experiments. The results from these two experiments suggest that inhibition of aromatase activity by AI could influence sex differentiation in bluegill sunfish. [source] Morphological sex change upon treatment by endocrine modulators in meiogynogenetic tench (Tinca tinca L.)AQUACULTURE RESEARCH, Issue 2 2010Martin Hulak Abstract Exogenous steroids alter sex differentiation in fish substantially. In the present study we have evaluated the effects of 17,-methyltestosterone (MT) and oestrogen receptor antagonist Tamoxifen (TA) on gonadal development and skewness of the sex ratio in all-female tench juveniles. In the first two experiments, sexually undifferentiated juveniles were orally treated with three doses of MT and TA (50, 100 and 150 mg kg,1). Both the treatments resulted in a moderate dose-dependent masculinization, with neomale production ranging from 17% (50 mg kg,1) to 26% (150 mg kg,1) for the MT only treatment, and from 0% (50 mg kg,1) to 27% (100 mg kg,1) only for the TA treatment respectively. In the third experiment treatment of sexually differentiated tench females with single steroid treatments or combinations of the two resulted in populations composed of females and intersex individuals. The significantly highest occurrence of intersex individuals (45.5%) was found in the group subjected to combine treatment of MT+TA (150+200 mg kg,1). No masculinization effect of the single or the combined treatment occurred. It can be concluded that oral treatment with MT or TA only slightly modifies the normal process of sex differentiation in gynogenetic tench juvenile, but treatment with the above-mentioned combinations has a highly significant potential to skew the sex ratio in sexually differentiated tench females. However, from an applied point of view, the treatment procedure will need optimization before use at a commercial level. [source] The effects of temperature on sex differentiation and growth of black sea bass (Centropristis striata L.)AQUACULTURE RESEARCH, Issue 6 2009Heidi R Colburn Abstract To examine the effects of temperature on sex differentiation in the black sea bass (Centropristis striata L.), a protogynous hermaphrodite, juveniles (,0.5 g) were cultured in recirculating systems at 17, 21 or 25 °C. Growth was assessed at 155, 182, 241 and 275 days post hatch and sex differentiation was determined histologically. No differences were found in the sex ratios of fish reared at different temperatures, but only 55,64% developed as females. Growth was significantly greater in males across all temperature treatments. These results suggest that black sea bass exhibit sexually dimorphic growth patterns and that female-specific sex determination can be disrupted in culture. [source] Environmental sex determination, external sex differentiation and structure of the androgenic gland in the Pacific white shrimp Litopenaeus vannamei (Boone)AQUACULTURE RESEARCH, Issue 15 2006Rafael Campos-Ramos Abstract Environmental effects on sex determination in Litopenaeus vannamei were studied by rearing day 1 postlarvae at three temperatures, under three photoperiods, at high density and by starving. None of the environmental conditions affected sex determination or differential development of gender in this species. From day 50, the development of the endopodite of the first pair of pleopods revealed the first external differentiation, showing a triangular structure with three setae in females, whereas a tubular structure remained in males. Juvenile shrimp sex differentiation took place from days 50,90, independent of size, only if postlarvae reached a development threshold of 150 mg of body weight and 20 mm of body length previously. Histology and scanning electron microscopy of the vas deferens revealed that the androgenic gland (AG) is a single 2-mm cord attached in the subterminal ejaculatory region, just before the distal vas deferens narrows. The AG is composed of large oval cells containing vacuolated cytoplasm, and each cell has a prominent rounded nucleus, similar to all descriptions of the AG in Malacostracans, so we assume that it should have the same function in sex differentiation. [source] The androgenic gland and monosex culture of freshwater prawn Macrobrachium rosenbergii (De Man): a biotechnological perspectiveAQUACULTURE RESEARCH, Issue 3 2005Amir Sagi Abstract Males of the freshwater prawn Macrobrachium rosenbergii (De Man) grow faster and reach a larger size at harvest than females of the species. It is thus obvious that culture of monosex all-male populations would be economically advantageous. Sexual differentiation in crustaceans is regulated by the androgenic gland (AG), which plays a pivotal role in the regulation of male differentiation and in the inhibition of female differentiation. In M. rosenbergii, AG removal from immature males resulted in sex reversal, with complete female differentiation. Similarly, AG implantations into immature females lead to the development of the male reproductive system. Sex-reversed M. rosenbergii animals were capable of mating with normal specimens to produce offspring. Early attempts in Israel and more recently, attempts in other countries to establish all-male populations through manual segregation showed that for the production of monosex prawn populations to be economically feasible, intervention via the AG is probably required. However, a suitable biotechnology is still to be developed, and an androgenic hormone has yet to be identified in decapods. Three lines of aquacultural and biotechnological research and development are proposed for the future: (1) Establishment of monosex cultures through manual segregation, together with the application of selective harvesting and claw ablation, as well as examination of different monosex culture strategies under a variety of economic conditions. (2) Microsurgical intervention in the AG, leading to the development of functional neo-females, which would subsequently be mated with normal males to produce all-male progeny. (3) Elucidation of AG bioactive products to enable biochemical or molecular manipulation of sex differentiation. [source] The chromosome 7q region association with rheumatoid arthritis in females in a british population is not replicated in a North American case,control seriesARTHRITIS & RHEUMATISM, Issue 1 2009Benjamin D. Korman Objective The single-nucleotide polymorphism (SNP) rs11761231 on chromosome 7q has been reported to be sexually dimorphic marker for rheumatoid arthritis (RA) susceptibility in a British population. We sought to replicate this finding and to better characterize susceptibility alleles in the region in a North American population. Methods DNA from 2 North American collections of RA patients and controls (1,605 cases and 2,640 controls) was genotyped for rs11761231 and 16 additional chromosome 7q tag SNPs using Sequenom iPlex assays. Association tests were performed for each collection and also separately, contrasting male cases with male controls and female cases with female controls. Principal components analysis (EigenStrat) was used to determine association with RA before and after adjusting for population stratification in the subset of the samples for which there were whole-genome SNP data (772 cases and 1,213 controls). Results We failed to replicate an association of the 7q region with RA. Initially, rs11761231 showed evidence for association with RA in the North American Rheumatoid Arthritis Consortium (NARAC) collection (P = 0.0073), and rs11765576 showed association with RA in both the NARAC (P = 0.038) and RA replication (P = 0.0013) collections. These markers also exhibited sex differentiation. However, in the whole-genome subset, neither SNP showed significant association with RA after correction for population stratification. Conclusion While 2 SNPs on chromosome 7q appeared to be associated with RA in a North American cohort, the significance of this finding did not withstand correction for population substructure. Our results emphasize the need to carefully account for population structure to avoid false-positive disease associations. [source] | ||||||||||||||||