Ana Elisa C. Billerbeck

Founder effect for the highly prevalent R337H mutation of tumor suppressor p53 in Brazilian patients with adrenocortical tumors

The incidence of adrenocortical tumors in children from the Southern region of Brazil is higher than in other parts of the world. This fact has been related to the identification of an inherited missense mutation of the p53 (R337H) at high frequency (78-97%) in Brazilian children with adrenocortical tumors. Given the high frequency of this germline mutation in the Brazilian population, it is very likely that the R337H mutation has arisen from a common origin. In this study, we analyzed two highly polymorphic intragenic markers (VNTRp53 and p53CA) in 22 patients (16 children and 6 adults) with adrenocortical tumors carrying the germline R337H mutation and 60 normal individuals using GeneScan Fragment Analysis software. We found six and sixteen different alleles for the VNTRp53 and p53CA polymorphic markers, respectively. Two distinct alleles, both with 122 bp, were found in 56.8% (VNTRp53) and 54.5% (p53CA) of the 44 alleles from patients with adrenocortical tumors associated with the R337H mutation. Differently, these same VNTRp53 and p53CA alleles were found in 18.3% and 14.2% of 120 alleles from normal individuals, respectively (p<0.01, Chi-square test). An identical haplotype for p53 locus was also identified in 95% of the apparently unrelated Brazilian patients with adrenocortical tumors carrying the R337H mutation. In conclusion, we demonstrated a strong evidence of co-segregation between two intragenic polymorphic p53 markers and the germline R337H mutation, indicating that this mutation has originated from a single common ancestral in the great majority of the Brazilian patients with adrenocortical tumors.

Influence of different genotypes on 17‐hydroxyprogesterone levels in patients with nonclassical congenital adrenal hyperplasia due to 21‐hydroxylase deficiency

The diagnosis of the nonclassical form of 21‐hydroxylase (NC‐21OH) deficiency, established before molecular studies, is based on basal 17OH‐progesterone (17OH‐P) values > 15 nmol/l or ACTH‐stimulated 17OH‐P values > 30 nmol/l. This disease is caused by mutations in the structural gene that can be grouped into three categories: A, B and C, according to the predicted level of enzymatic activity. So, the genotype of the nonclassical form is a combination of mutations that cause moderate impairment of enzymatic activity in one allele and mutations which cause total (A), severe (B: 3%) or moderate (C: 20–60%) impairment of enzymatic activity in the other allele.

A novel missense mutation (S18N) in the 5' non-HMG box region of the SRY gene in a patient with partial gonadal dysgenesis and his normal male relatives

Abstract Mutations in the sex-determining region of the Y chromosome (the SRY gene) have been reported in low frequency in patients with 46,XY gonadal dysgenesis. We investigated 21 Brazilian 46,XY sex-reversed patients, who presented either complete or partial gonadal dysgenesis or embryonic testicular regression syndrome. Using Southern blotting, polymerase chain reaction, denaturing gradient gel electrophoresis and direct sequencing, we analyzed deletions and point mutations in the SRY gene. We found a missense mutation at codon 18 upstream of the 5′ border of the HMG box of the SRY gene in one patient with partial gonadal dysgenesis. This variant sequence was also found in DNA obtained from blood and sperm cells of his father and in blood cells of his normal brother. The S18N mutation was not found in 50 normal males, ruling out the possibility of a common polymorphism. We identified a novel familial missense mutation (S18N) in the 5’ non-HMG box of the SRY gene in 1 of 21 patients with 46,XY sex reversal.

SHOX mutations in idiopathic short stature and Leri‐Weill dyschondrosteosis: frequency and phenotypic variability

Objective  The frequency of SHOX mutations in children with idiopathic short stature (ISS) has been found to be variable. We analysed the SHOX gene in children with ISS and Leri‐Weill dyschondrosteosis (LWD) and evaluated the phenotypic variability in patients harbouring SHOX mutations.

Low Frequency of CYP21B Deletions in Brazilian Patients with Congenital Adrenal Hyperplasia Due to 21-Hydroxylase Deficiency

The frequency of large mutations was determined in 131 Brazilian patients with different clinical forms of 21-hydroxylase deficiency, belonging to 116 families. DNA samples were examined by Southern blotting hybridization with genomic CYP21 and C4cDNA probes after TaqI and BglII restriction. Large gene conversions were found in 6.6% and CYP21B deletions in 4.4% of the alleles. The breakpoint in these hybrid genes occurred after exon 3 in 92% of the alleles. All rearrangements involving CYP21B gene occurred in the heterozygous form, except in a patient with simple virilizing form who presented homozygous CYP21B deletion. Our data showed that in these Brazilian patients, CYP21B deletions were less frequent than in most of the large series previously reported.

The degree of external genitalia virilization in girls with 21-hydroxylase deficiency appears to be influenced by the CAG repeats in the androgen receptor gene

Background  Women with 21‐hydroxylase deficiency present much variability in external genitalia virilization, even among those with similar impairments of 21‐hydroxylase (21OH) activity.

Combined pituitary hormone deficiency (CPHD) due to a complete PROP1 deletion

Objective  PROP1 mutations are the most common cause of genetic combined pituitary hormone deficiency (CPHD). The aim of this study was to investigate the PROP1 gene in two siblings with CPHD.

Investigation of the ZFY gene in XX true hermaphroditism and Swyer syndrome

SummaryFour patients with 46,XX true hermaphroditism and one patient with 46,XY pure gonadal dysgenesis (Swyer syndrome) were analyzed with a Y chromosome-derived probe that detects a specific fragment on the short arm of the Y chromosome in the putative testicle-determining region and also a fragment on the short arm of the X chromosome. Normal males and females, an individual with Turner syndrome, and patients with various causes of anomalous gonadal differentiation accompanied by cytogenetically present Y chromosome were used as controls. The Y-specific fragment was not detected in any of the persons with 46,XX true hermaphroditism. However, this fragment was positive in the 46,XY female and in all Y-bearing patients. Cytogenetic and molecular absence of the ZFY sequence in 46,XX true hermaphrodites calls for explanations other than the classic embryogenie theory. The absence of testicular differentiation in the ZFY-positive XY female evidences functionally altered sex determination or, alternatively, defective gonadal receptors.

Estudo multicêntrico de pacientes brasileiros com deficiência da 21-hidroxilase: correlação do genótipo com o fenótipo

ABSTRACT Multicentric Study of Brazilian Patients With 21-Hydroxylase Defi-ciency: A Genotype-Phenotype Correlation. We analyzed the clinical and molecular data of 205 patients with thethree different clinical forms of 21-hydroxylase deficiency, in whom theclinical and molecular diagnosis were already defined. The most fre-quent mutations were I2 splice in the salt wasting form, I172N in the sim-ple virilizing and V281L in the nonclassical form, presenting similar fre-quencies as those observed in other populations. We found a lower fre-quency of 21-hydroxylase gene deletion, similar to that previously iden-tified in Argentinean and Mexican populations. Five new mutations weredescribed in our population: G424S, H28+C, Ins 1003^1004 A, R408C andIVS2-2A>G. The genotype was classified in three groups according to theimpairment of enzymatic activity observed in vitro , Group A: 0-2%, GroupB: 3-7% and Group C: >20%. Group A mutations correlated with the saltwasting form, the Group B with simple virilizing form and Group C withthe non classical form. The severity of genotype showed a positive cor-

Substitutions in the CYP21A2 promoter explain the simple‐virilizing form of 21‐hydroxylase deficiency in patients harbouring a P30L mutation

The classical and nonclassical phenotypes of 21‐hydroxylase deficiency represent a continuous spectrum of the impairment of 21‐hydroxylase activity due to mutations between the CYP21A2 gene. These mutations occur mainly by microconversion in the homologous nonfunctional CYP21A1P gene. The P30L mutation is associated with the nonclassical form, and it reduces the activity to 30–40% of the normal enzyme. We have described three female patients exhibiting a simple virilizing phenotype and bearing the P30L mutation in compound heterozygosis with a severe mutation. To identify additional mutations causing this phenotype, the promoter region was sequenced and four mutations were identified: −126C → T, −113G → A, −110T → C and −103 A → G. These substitutions are normally present in the promoter region of the pseudogene and in vitro studies demonstrated that they reduced the transcriptional activity fivefold. They might have been converted to the CYP21A2 promoter together with the P30L mutation in these patients. Therefore, these substitutions in synergism with the P30L mutation might decrease the enzyme activity resulting in a more severe phenotype, and a DNA sequence of −167 bases of the CYP21A2 gene should be performed in patients with 21‐hydroxylase deficiency in whom the phenotype is more severe than predicted by the genotype.