A study of splicing mutations in disorders of sex development.

The presence of splicing sequence variants in genes responsible for sex development in humans may compromise correct biosynthesis of proteins involved in the normal development of gonads and external genitalia. In a cohort of Brazilian patients, we identified mutations in HSD17B3 and SRD5A2 which are both required for human sexual differentiation. A number of these mutations occurred within regions potentially critical for splicing regulation. Minigenes were used to validate the functional effect of mutations in both genes. We evaluated the c.277 + 2 T > G mutation in HSD17B3, and the c.544 G > A, c.548-44 T > G and c.278delG mutations in SRD5A2. We demonstrated that these mutations altered the splicing pattern of these genes. In a genomic era these results illustrate, and remind us, that sequence variants within exon-intron boundaries, which are primarily identified for diagnostic purposes and have unknown pathogenicity, need to be assessed with regards to their impact not only on protein expression, but also on mRNA splicing.

The novel p.Cys65Tyr mutation in NR5A1 gene in three 46,XY siblings with normal testosterone levels and their mother with primary ovarian insufficiency.

BACKGROUND: Disorders of sex development (DSD) is the term used for congenital conditions in which development of chromosomal, gonadal, or phenotypic sex is atypical. Nuclear receptor subfamily 5, group A, member 1 gene (NR5A1) encodes steroidogenic factor 1 (SF1), a transcription factor that is involved in gonadal development and regulates adrenal steroidogenesis. Mutations in the NR5A1 gene may lead to different 46,XX or 46,XY DSD phenotypes with or without adrenal failure. We report a Brazilian family with a novel NR5A1 mutation causing ambiguous genitalia in 46,XY affected individuals without Müllerian derivatives and apparently normal Leydig function after birth and at puberty, respectively. Their mother, who is also heterozygous for the mutation, presents evidence of primary ovarian insufficiency. CASE PRESENTATION: Three siblings with 46,XY DSD, ambiguous genitalia and normal testosterone production were included in the study. Molecular analyses for AR, SRD5A2 genes did not reveal any mutation. However, NR5A2 sequence analysis indicated that all three siblings were heterozygous for the p.Cys65Tyr mutation which was inherited from their mother. In silico analysis was carried out to elucidate the role of the amino acid change on the protein function. After the mutation was identified, all sibs and the mother had been reevaluated. Basal hormone concentrations were normal except that ACTH levels were slightly elevated. After 1 mcg ACTH stimulation test, only the older sib showed subnormal cortisol response. CONCLUSION: The p.Cys65Tyr mutation located within the second zinc finger of DNA binding domain was considered deleterious upon analysis with predictive algorithms. The identification of heterozygous individuals with this novel mutation may bring additional knowledge on structural modifications that may influence NR5A1 DNA-binding ability, and may also contribute to genotype-phenotype correlations in DSD. The slightly elevated ACTH basal levels in all three patients with 46,XY DSD and the subnormal cortisol response after 1 mcg ACTH stimulation in the older sib indicate that a long-term follow-up for adrenal function is important for these patients. Our data reinforce that NR5A1 analysis must also be performed in 46,XY DSD patients with normal testosterone levels without AR mutations.

Clinical and molecular spectrum of patients with 17β-hydroxysteroid dehydrogenase type 3 (17-β-HSD3) deficiency / Espectro clínico e molecular de pacientes com deficiência de 17β-hidroxiesteroide desidrogenase tipo 2 (17-β-HSD3)

The enzyme 17β-hydroxysteroid dehydrogenase type 3 (17-β-HSD3) catalyzes the conversion of androstenedione to testosterone in the testes, and its deficiency is a rare disorder of sex development in 46,XY individuals. It can lead to a wide range of phenotypic features, with variable hormonal profiles. We report four patients with the 46,XY karyotype and 17-β-HSD3 deficiency, showing different degrees of genital ambiguity, increased androstenedione and decreased testosterone levels, and testosterone to androstenedione ratio < 0.8. In three of the patients, diagnosis was only determined due to the presence of signs of virilization at puberty. All patients had been raised as females, and female gender identity was maintained in all of them. Compound heterozygosis for c.277+2T>G novel mutation, and c.277+4A>T mutation, both located within the intron 3 splice donor site of the HSD17B3 gene, were identified in case 3. In addition, homozygosis for the missense p.Ala203Val, p.Gly289Ser, p.Arg80Gln mutations were found upon HSD17B3 gene sequencing in cases 1, 2, and 4, respectively. Arq Bras Endocrinol Metab. 2012;56(8):533-9.

A enzima 17β-hidroxiesteroide desidrogenase tipo 3 (17-β-HSD3) catalisa a conversão de androstenediona a testosterona nos testículos, e sua deficiência é uma forma rara de distúrbio do desenvolvimento do sexo em indivíduos 46,XY. A desordem apresenta um amplo espectro de características fenotípicas e de resultados de dosagens laboratoriais. Neste trabalho, são relatados quatro casos de deficiência da 17-β-HSD3 com cariótipo 46,XY, ambiguidade genital em diversos graus, androstenediona aumentada, testosterona diminuída, e relação testosterona e androstenediona < 0,8. Em três das pacientes, o diagnóstico foi suspeitado devido à presença de sinais de virilização na puberdade. Todos os pacientes foram criados como mulheres, e a identidade de gênero feminino foi mantida em todas elas. A heterozigose composta da mutação nova c.277+2T>G e da mutação c.277+4A>T, ambas localizadas no sítio doador de splicing do íntron 3 do gene HSD17B3, foi identificada no caso 3. Além dessas, as mutações missense p.Ala203Val, p.Gly289Ser, p.Arg80Gln foram identificadas em homozigose pelo sequenciamento do gene HSD17B3 dos casos 1, 2 e 4, respectivamente. Arq Bras Endocrinol Metab. 2012;56(8):533-9.

Clinical and molecular spectrum of patients with 17ß-hydroxysteroid dehydrogenase type 3 (17-ß-HSD3) deficiency.

The enzyme 17ß-hydroxysteroid dehydrogenase type 3 (17-ß-HSD3) catalyzes the conversion of androstenedione to testosterone in the testes, and its deficiency is a rare disorder of sex development in 46,XY individuals. It can lead to a wide range of phenotypic features, with variable hormonal profiles. We report four patients with the 46,XY karyotype and 17-ß-HSD3 deficiency, showing different degrees of genital ambiguity, increased androstenedione and decreased testosterone levels, and testosterone to androstenedione ratio < 0.8. In three of the patients, diagnosis was only determined due to the presence of signs of virilization at puberty. All patients had been raised as females, and female gender identity was maintained in all of them. Compound heterozygosis for c.277+2T>G novel mutation, and c.277+4A>T mutation, both located within the intron 3 splice donor site of the HSD17B3 gene, were identified in case 3. In addition, homozygosis for the missense p.Ala203Val, p.Gly289Ser, p.Arg80Gln mutations were found upon HSD17B3 gene sequencing in cases 1, 2, and 4, respectively.

Clinical and Laboratorial Features That May Differentiate 46,XY DSD due to Partial Androgen Insensitivity and 5α-Reductase Type 2 Deficiency.

The aim of this study was to search for clinical and laboratorial data in 46,XY patients with ambiguous genitalia (AG) and normal testosterone (T) synthesis that could help to distinguish partial androgen insensitivity syndrome (PAIS) from 5α-reductase type 2 deficiency (5α-RD2) and from cases without molecular defects in the AR and SRD5A2 genes. Fifty-eight patients (51 families) were included. Age at first evaluation, weight and height at birth, consanguinity, familial recurrence, severity of AG, penile length, LH, FSH, T, dihydrotestosterone (DHT), Δ4-androstenedione (Δ4), and T/DHT and T/Δ4 ratios were evaluated. The AR and SRD5A2 genes were sequenced in all cases. There were 9 cases (7 families) of 5α-RD2, 10 cases (5 families) of PAIS, and 39 patients had normal molecular analysis of SRD5A2 and AR genes. Age at first evaluation, birth weight and height, and T/DHT ratio were lower in the undetermined group, while penile length was higher in this group. Consanguinity was more frequent and severity of AG was higher in 5α-RD2 patients. Familial recurrence was more frequent in PAIS patients. Birth weight and height, consanguinity, familial recurrence, severity of AG, penile length, and T/DHT ratio may help the investigation of 46,XY patients with AG and normal T synthesis.

Molecular diagnosis of 5α-reductase type II deficiency in Brazilian siblings with 46,XY disorder of sex development.

The steroid 5α-reductase type II enzyme catalyzes the conversion of testosterone (T) to dihydrotestosterone (DHT), and its deficiency leads to undervirilization in 46,XY individuals, due to an impairment of this conversion in genital tissues. Molecular analysis in the steroid 5α-reductase type II gene (SRD5A2) was performed in two 46,XY female siblings. SRD5A2 gene sequencing revealed that the patients were homozygous for p.Gln126Arg missense mutation, which results from the CGA > CAA nucleotide substitution. The molecular result confirmed clinical diagnosis of 46,XY disorder of sex development (DSD) for the older sister and directed the investigation to other family members. Studies on SRD5A2 protein structure showed severe changes at NADPH binding region indicating that structural modeling analysis can be useful to evaluate the deleterious role of a mutation as causing 5α-reductase type II enzyme deficiency.