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Line Homozygous (line + homozygous)
Selected AbstractsLoss-of-function variants of the human melanocortin-1 receptor gene in melanoma cells define structural determinants of receptor functionFEBS JOURNAL, Issue 24 2002Jesús Sánchez Más The ,-melanocyte-stimulating hormone (,MSH) receptor (MC1R) is a major determinant of mammalian skin and hair pigmentation. Binding of ,MSH to MC1R in human melanocytes stimulates cell proliferation and synthesis of photoprotective eumelanin pigments. Certain MC1R alleles have been associated with increased risk of melanoma. This can be theoretically considered on two grounds. First, gain-of-function mutations may stimulate proliferation, thus promoting dysplastic lesions. Second, and opposite, loss-of-function mutations may decrease eumelanin contents, and impair protection against the carcinogenic effects of UV light, thus predisposing to skin cancers. To test these possibilities, we sequenced the MC1R gene from seven human melanoma cell (HMC) lines and three giant congenital nevus cell (GCNC) cultures. Four HMC lines and two GCNC cultures contained MC1R allelic variants. These were the known loss-of-function Arg142His and Arg151Cys alleles and a new variant, Leu93Arg. Moreover, impaired response to a superpotent ,MSH analog was demonstrated for the cell line carrying the Leu93Arg allele and for a HMC line homozygous for wild-type MC1R. Functional analysis in heterologous cells stably or transiently expressing this variant demonstrated that Leu93Arg is a loss-of-function mutation abolishing agonist binding. These results, together with site-directed mutagenesis of the vicinal Glu94, demonstrate that the MC1R second transmembrane fragment is critical for agonist binding and maintenance of a resting conformation, whereas the second intracellular loop is essential for coupling to the cAMP system. Therefore, loss-of-function, but not activating MC1R mutations are common in HMC. Their study provides important clues to understand MC1R structure-function relationships. [source] The whorl-specific action of a petunia class B floral homeotic geneGENES TO CELLS, Issue 2 2000Suguru Tsuchimoto Background GREEN PETAL (GP) is thought to be a petunia class B floral homeotic gene, because the gp mutant flower displays a severe homeotic conversion of petals into sepals in the second whorl. However, since the third whorl stamens remain unaffected in the gp null mutant, gp is different from class B mutants in Arabidopsis and Antirrhinum, which also show a conversion of the third whorl stamens into the carpelloid tissue. BLIND (BL) is thought to be a petunia class A floral homeotic gene, because the bl mutant flower displays homeotic conversions of sepals into the stigmatoid tissue in the first whorl and of the corolla limb into antheroid structures in the second whorl. Results A double mutant line homozygous for both bl and gp mutations was constructed. The bl gp double mutant flower displays homeotic conversions of sepals into the stigmatoid tissue in the first whorl and of the corolla limb into antheroid structures with stigmatoid tips in the second whorl. In the third and fourth whorls of the mutant flower, organs remained unchanged. In the gp flower, a petunia B-type gene FBP1 is expressed strongly in the third whorl organs, but much more weakly in the second whorl organs. In the bl gp flower, FBP1 was found to be expressed strongly in the second whorl organs as well as in the third whorl organs. Conclusions Petunia has a class B gene other than GP that determines organ identities, both in the second and third whorls of the double mutant flower, and the action of the postulated class B gene (here called PhBX) is prevented by the BL gene in the second whorl of the gp flower. PhBX appears to be a gene that specifically interacts with the FBP1 gene, and is involved in the up-regulation of FBP1. [source] C1473G polymorphism in mouse tph2 gene is linked to tryptophan hydroxylase-2 activity in the brain, intermale aggression, and depressive-like behavior in the forced swim testJOURNAL OF NEUROSCIENCE RESEARCH, Issue 5 2009Daria V. Osipova Abstract Tryptophan hydroxylase-2 (TPH2) is the rate-limiting enzyme of brain serotonin synthesis. The C1473G polymorphism in the mouse tryptophan hydroxylase-2 gene affects the enzyme's activity. In the present study, we investigated the linkage between the C1473G polymorphism, enzyme activity in the brain, and behavior in the forced swim, intermale aggression, and open field tests using mice of the C57BL/6 (C/C) and CC57BR/Mv (G/G) strains and the B6-1473C (C/C) and B6-1473G (G/G) lines created by three successive backcrossings on C57BL/6. Mice of the CC57BR/Mv strain had decreased brain enzyme activity, aggression intensity, and immobility in the forced swim test, but increased locomotor activity and time spent in the central part of the open field arena compared with animals of the C57BL/6 strain. Mice of the B6-1473G line homozygous for the 1473G allele had lower TPH2 activity in the brain, aggression intensity, and immobility time in the forced swim test compared with animals of the B6-1473C line homozygous for the 1473C allele. No differences were found between the B6-1473G and B6-1473C mice in locomotor activity and time spent in the central part of the arena in the open field test. Thus, the C1473G polymorphism is involved in the determination of TPH2 activity and is linked to aggression intensity and forced-swim immobility in mice. At the same time, the polymorphism does not affect locomotion and anxiety-related behavior in the open field test. The B6-1473C and B6-1473G mice represent a valuable experimental model for investigating molecular mechanisms of serotonin-related behavior. © 2008 Wiley-Liss, Inc. [source] Spectrum of mutations in MMACHC, allelic expression, and evidence for genotype,phenotype correlations,HUMAN MUTATION, Issue 7 2009Jordan P. Lerner-Ellis Abstract Methylmalonic aciduria and homocystinuria, cblC type, is a rare disorder of intracellular vitamin B12 (cobalamin [Cbl]) metabolism caused by mutations in the MMACHC gene. MMACHC was sequenced from the gDNA of 118 cblC individuals. Eleven novel mutations were identified, as well as 23 mutations that were observed previously. Six sequence variants capture haplotype diversity in individuals across the MMACHC interval. Genotype,phenotype correlations of common mutations were apparent; individuals with c.394C>T tend to present with late-onset disease whereas patients with c.331C>T and c.271dupA tend to present in infancy. Other missense variants were also associated with late- or early-onset disease. Allelic expression analysis was carried out on human cblC fibroblasts compound heterozygous for different combinations of mutations including c.271dupA, c.331C>T, c.394C>T, and c.482G>A. The early-onset c.271dupA mutation was consistently underexpressed when compared to control alleles and the late-onset c.394C>T and c.482G>A mutations. The early-onset c.331C>T mutation was also underexpressed when compared to control alleles and the c.394C>T mutation. Levels of MMACHC mRNA transcript in cell lines homozygous for c.271dupA, c.331C>T, and c.394C>T were assessed using quantitative real-time RT-PCR. Cell lines homozygous for the late onset c.394C>T mutation had significantly higher levels of transcript when compared to cell lines homozygous for the early-onset mutations. Differential or preferential MMACHC transcript levels may provide a clue as to why individuals carrying c.394C>T generally present later in life. Hum Mutat 30:1,10, 2009. © 2009 Wiley-Liss, Inc. [source] | ||||||||||