Molecular analysis of CYP21 and C4 genes in Brazilian families with the classical form of steroid 21-hydroxylase deficiency

The most common enzymatic defect of steroid synthesis is deficiency of the adrenal steroid 21-hydroxylase. Inhibition of the formation of cortisol results in an increased pituitary release of ACTH which in turn drives the adrenal cortex to overproduce androgens. This hormonal setting affects the development of genetic females by misdirecting the differentiation of external genitalia towards the male type. Since the isolation of the gene encoding 21-hydroxylase enzyme in 1984, gene deletions, large gene conversions, and microconversions have been reported to be responsible for the disease. In this paper, we report a study of this genetic defect in 22 families with one or more affected offspring diagnosed as having the classical form of congenital adrenal hyperplasia. The DNA from 30 patients was analyzed with three restriction enzymes. Hybridization with a 21-hydroxylase cDNA probe and the 5' end of a C4 genomic probe disclosed gene deletion in 7.3 percent (3/41) of the disease-related chromosomes. The rate of large gene conversion was 17.1 percent (7/41), and no abnormality in the hybridization pattern was observed in 75.6 percent (31/41) of the disease alleles. Densitometry of the autoradiographs was used to determine the ratio of the copy-number of the 2 1-hydroxylase gene (CYP21B) to the copy-number of its pseudogene (CYP21A). Differences in phenotype, the low frequency of gene deletion, and the high frequency of gene conversion compared with other studies in different populations indicated that 21-hydroxylase deficiency in the Brazilian population may involve different molecular mutations.

Use of y-chromosome-specific DNA probes to evaluate an XX male

The function of a Y human chromosomal DNA sequence was evaluated. The Y-5 probe was isolated from a flow-sorted chromosome library and detects Y-specific sequences. The Y-5 probe and other T-specific probes were used to analyze an XX male patient without ambiguous genitalia. DNA sequences from the short arm of the chromosome Y that were detected with pDP1007 and DP105 in the patient's genome explain the testis differentation observed in this case. Failure of the patient's DNA to hybridize to the Y-5 probe shows that the primitive gonads can differentiate into testes even in the absence of this chromosome region. In contrast, a gene controlling spermatogenesis may exist in this region because the patient azoospermic

The in vivo effect of cobalt chloride on chromosomes.

Este trabalho apresenta o estudo cromossomico de celulas somaticas e germinativas de hamsters machos (Mesocricetus auratus, 2n = 44) com 6 a 16 semanas de idade. As analises das celulas somaticas foram realizadas em preparacoes citologicas da medula ossea de 13 animais controles e de 10 animais inoculados com solucao salina de cloreto de cobalto (CoCl2). Para obtencao de metafases meioticas, foram feitas preparacoes citologicas de 6 animais de cada grupo. Somente os animais tratados com CoCl2 mostraram celulas somaticas e espermatocitos resultantes da meiose I, com aumento significativo de hiperdiploidia e pseudodiploidia