Novel deletion alleles carrying CYP21A1P/A2 chimeric genes in Brazilian patients with 21-hydroxylase deficiency.

BACKGROUND: Congenital adrenal hyperplasia due to 21-hydroxylase deficiency is caused by deletions, large gene conversions or mutations in CYP21A2 gene. The human gene is located at 6p21.3 within a locus containing the genes for putative serine/threonine Kinase RP, complement C4, steroid 21-hydroxylase CYP21 tenascin TNX, normally, in a duplicated cluster known as RCCX module. The CYP21 extra copy is a pseudogene (CYP21A1P). In Brazil, 30-kb deletion forming monomodular alleles that carry chimeric CYP21A1P/A2 genes corresponds to ~9% of disease-causing alleles. Such alleles are considered to result from unequal crossovers within the bimodular C4/CYP21 locus. Depending on the localization of recombination breakpoint, different alleles can be generated conferring the locus high degree of allelic variability. The purpose of the study was to investigate the variability of deleted alleles in patients with 21-hydroxylase deficiency. METHODS: We used different techniques to investigate the variability of 30-kb deletion alleles in patients with 21-hydroxylase deficiency. Alleles were first selected after Southern blotting. The composition of CYP21A1P/A2 chimeric genes was investigated by ASO-PCR and MLPA analyses followed by sequencing to refine the location of recombination breakpoints. Twenty patients carrying at least one allele with C4/CYP21 30-kb deletion were included in the study. RESULTS: An allele carrying a CYP21A1P/A2 chimeric gene was found unusually associated to a C4B/C4A Taq I 6.4-kb fragment, generally associated to C4B and CYP21A1P deletions. A novel haplotype bearing both p.P34L and p.H62L, novel and rare mutations, respectively, was identified in exon 1, however p.P30L, the most frequent pseudogene-derived mutation in this exon, was absent. Four unrelated patients showed this haplotype. Absence of p.P34L in CYP21A1P of normal controls indicated that it is not derived from pseudogene. In addition, the combination of different approaches revealed nine haplotypes for deleted 21-hydroxylase deficiency alleles. CONCLUSIONS: This study demonstrated high allelic variability for 30-kb deletion in patients with 21-hydroxylase deficiency indicating that a founder effect might be improbable for most monomodular alleles carrying CYP21A1P/A2 chimeric genes in Brazil.

Molecular analysis of KAL-1, GnRH-R, NELF and EBF2 genes in a series of Kallmann syndrome and normosmic hypogonadotropic hypogonadism patients.

We report the results of molecular analysis in a series of twelve Kallmann syndrome (KS) and five normosmic hypogonadotropic hypogonadism (nHH) Brazilian patients. Kallman syndrome 1 (KAL-1) gene analysis was performed in all patients and the gonadotrophin releasing hormone receptor (GnRH-R) gene was investigated in nHH patients using PCR analysis with exon-flanking primers followed by automated sequencing techniques. Two-point mutations at the KAL-1 locus were found in two KS patients. One case exhibited a novel C deletion (del1956C) in exon 12 leading to a premature stop codon at position 617. The second case, a C to T transition at exon 5, showed a stop codon at aminoacid 191 (Arg191X). Renal agenesis and bimanual synkinesis, which are frequently found in patients with the KAL-1 mutation, were observed in these cases. Among the KS patients, two previously reported cases had intragenic deletions of exons 5-10, while a third patient had a KAL-1 gene microdeletion detected by fluorescence in situ hybridization. For the nHH patients, no abnormalities were observed at the exonic and flanking sequences of the KAL-1 or GnRH-R genes. Nasal embryonic LHRH factor (NELF) and early B-cell factor 2 (EBF2) exons were evaluated in KAL-1/GnRH-R mutation-negative cases (seven KS and five nHH) by sequence analysis but no mutations were identified in the coding regions in these patients. In conclusion, this report includes the description of a novel point mutation of the KAL-1 gene and suggests that the KAL-1 mutations and deletions might be more prevalent in KS Brazilian patients than previously described in other series. NELF and EBF2 genes have been considered good candidates for HH and a large number of patients need to be studied to assess their contribution to reproductive function.

Bone mineralization in Turner syndrome: a transverse study of the determinant factors in 58 patients.

Turner syndrome (TS) is characterized by the presence of an X chromosome and total or partial loss of the second sex chromosome, short stature, hypergonadotrophic hypogonadism, and a variable dysmorphic picture. Delayed puberty and estrogen deficiency are some of the determinant factors of osteoporosis in TS, but the whether or not there is an intrinsic bone defect is still obscure. The aim of this study was to evaluate the correlation of the z score of bone mineral density (BMD) with age, weight, height, karyotype, associated diseases, bone age, and estrogen therapy in TS patients. We performed a transverse study with area BMD of L2-L4 with dual-energy X-ray absorptiometry (DEXA) in 58 patients with a cytogenetic diagnosis of TS, whose ages ranged from 5 to 29 years. It was observed that 86% of the patients presented with a BMD z score below -1 SD, and 46.5% with a value below -2.5 SD. There was a significant negative association of BMD with age and height, and a positive association with weight and bone mass index (BMI) z scores. A higher BMD was observed in patients with spontaneous puberty and in those with more than 2 years of hormone replacement. In conclusion, there was a high incidence of reduced bone mass among our patients, which was influenced by weight and BMI, by the use and the time of estrogen replacement, and by the presence of spontaneous puberty.

Frequency of 677C -> T and 1298A -> C polymorphisms in the 5, 10-methylenetetrahydrofolate reductase ( MTHFR ) gene in Turner syndrome individuals

Turner syndrome (TS) is an interesting model for investigating the association between methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and non-disjunction because of the high frequency of chromosomal mosaicism among patients with this syndrome. We determined the frequencies of MTHFR 677C -> T and 1298A -> C polymorphic mutations in 49 patients with TS and 200 control individuals. The frequency of the 677C -> T allele was 0.39 for patients and 0.29 for controls while that of the 1298A -> C allele was 0.28 for patients and 0.25 for controls. Genotype frequencies were shown to be different in patients and controls (chi2 = 12.143; p = 0.033), and this was attributable to the higher frequency of the C677C -> T /677C -> T genotype among TS patients. In homozygotes, this mutation might have an effect on somatic chromosome disjunction by decreasing MTHFR activity.

Cytogenetic analysis and detection of KAL-1 gene deletion with fluorescence in situ hybridization (FISH) in patients with Kalmann syndrome

Kallmann syndrome (KS) is a disease clinically characterized by the association of hypogonadotropic hypogonadism and anosmia or hyposmia, for which three modes of transmission have been described: X-linked, autosomal recessive and autosomal dominant. The KAL-1 gene, responsible for the X-linked form of the disease, has been isolated and its intron-exon organization determined. In this study, two families with X-linked KS and four sporadic male patients with hypogonadotropic hypogonadism and anosmia were cytogenetically investigated with high-resolution techniques and FISH. Chro-mosomal analysis did not reveal any rearrangements or deletions. Deletion of the KAL-1 gene was detected by FISH in only one sporadic patient with the typical features of KS and a high palate. Among the familial cases renal abnormalities and pes cavus deformity were observed.

Densidade mineral óssea: estudo transversal em pacientes com síndrome de Turner / Bone mineral density: transversal study in Turner's syndrome

A síndrome de Turner (ST) caracteriza-se pela perda parcial ou total de um dos cromossomos X, hipogonadismo hipergonadotrófico e baixa estatura. A maioria dos estudos de densidade mineral óssea (DMO) em ST atribuem a osteoporose à ausência do desenvolvimento puberal e ao hipoestrogenismo, enquanto o envolvimento das alteraçöes ósseas intrínsecas à ST permanece obscuro. O objetivo deste estudo foi verificar a associaçäo entre a DMO com as variáveis como idade cronológica e óssea, peso, altura, cariótipo, doenças associadas e reposiçäo estrogênìca em pacientes com ST. Realizou-se um estudo transversal da DMO areal de L2-L4 por DEXA em 34 pacientes com diagnóstico citogenético de ST. Encontrou-se diferença estatística em relaçäo à idade (as pacientes com z DMO < -2,5 eram as de idade mais avançada), à altura (as pacientes com z DMO < -2,5 eram as mais altas) e a reposiçäo estrogênica (o z DMO foi menor nas pacientes que necessitaram de reposiçäo hormonal). Sugere-se, portanto, que a idade e a reposiçäo estrogênica podem ser fatores associados à baixa DMO na ST.