Low incidence of androgen receptor mutation among Egyptian children with androgen resistance

In Egypt, disorders of sex development [DSD] constitute a significant entity among the birth defect list. Previous studies have reported that end organ androgen unresponsiveness, i.e. Androgen resistance, was the most prevalent underlying mechanism among Egyptian 46, XY DSD cases. Based on cytogenetic and hormonal diagnostic criteria as well as few sporadic case reports, it was proposed that androgen receptor [AR] defects [i.e. Androgen insensitivity syndrome [AIS], OMIM#300068] might constitute a major etiology within this category. However, this has never been systematically ascertained through an AR molecular diagnostic approach. The current study aimed to assess the role of AR mutations as an underlying etiology among a sample of Egyptian 46,XY DSD pediatric patients presenting with androgen end organ unresponsiveness. In the current study, 21 children [age <18years] with male undermasculinization due to androgen end organ unresponsiveness were selected from 46, XY DSD cases. The selection criteria included ambiguous genital phenotype or genitalia discordant to the genotypic sex; 46,XY Karyotype and normal testicular response to HCG stimulation in prepubertal -patients or normal basal testosterone [T] levels in postpubertal subjects. Molecular studies of the AR entailed PCR amplification for screening of major deletions/ insertions, single stranded conformational polymorphism [SSCP] screening for point mutations in the AR 2-8 exons followed by sequencing of these exons for all cases. The results showed that none had major deletions/insertions. Five exons out of 147 [3.4%] showed abnormal SSCP migrational patterns. Out of those 5, two mutations in two Egyptian patients were detected by sequencing. The first was R840G [Arginine 840 glycine], in exon 7 [The ligand binding domain]. The other was A596T [Alanine 596 Threonine] in exon 3 [The DNA binding domain]. This study shows that AR mutation is an uncommon underlying etiology among Egyptian paediatric 46,XY cases

Prenatal diagnosis of spinal muscular atrophy in Egyptian families

Spinal muscular atrophy [SMA] is the second most common autosomal recessive neuromuscular disorder and a common cause of infant disability and mortality. It affects the anterior horn cells of the spinal cord and motor cranial nuclei leading to bilateral progressive paralysis of peripheral muscle and death due to affection of respiratory muscles. SMA patients are classified into three clinical types based on age of onset and severity of symptoms. About 94% of patients have homozygous absence of exon 7 in the survival of motor neuron 1 [SMN1] gene [homozygous delta 7SMN1 mutation]. The neuronal apoptosis inhibitory protein [NAIP] gene was found to be more frequently deleted in the severest form of the disease [type I]. This study aimed to comment on the implementation of genetic counseling and prenatal diagnosis of SMA for 37 fetuses from 27 Egyptian couples at risk of having an affected child. The homozygous delta 7SMN1 mutation and the deletion of exon 5 of the NAIP gene were detected using PCR-RFLP and multiplex PCR methods; respectively. Five fetuses showed homozygous delta 7SMN1 mutation and deletion of NAIP gene exon 5. In conclusion, prenatal diagnosis is an important tool for accurate diagnosis and genetic counseling that help decision making in high risk families

Phenylalanine hydroxylase VNTR polymorphism patterns among Egyptian normal and phenylketonuric subjects

Analysis of the polymorphic variable number of tandem repeats [VNTR] is a powerful tool for detection of DNA variation among normal individuals within a population, as well as testing linkage to disease-underlying mutations in various ethnic groups. Phenylketonuria [PKU] is caused by mutations in the phenylalanine hydroxylase [PAH] gene, which has a VNTR region at the 3 end. In this work, we report on the PAH VNTR polymorphism patterns among a sample of the Egyptian population and a large number of PKU cases. The study included 77 normal subjects and 87 phenylketonuric probands. Genomic DNA was extracted from leukocytes using the salting out technique. DNA amplification using specific primers and the polymerase chain reaction was used to detect the various VNTR patterns. The VNTR heterozygosity index was 56% and 21% in the normal and PKU groups, respectively. The VNTR homozygosity index was comparably high in patients with IVS10-11 G>A and R261Q mutations, [i.e. > 80%]. An unusually high prevalence of the 8-RU and 10-RU alleles among non-IVS1011 G>A/non-R261Q PKU cases was noted. The VNTR patterns in both normal and PKU-affected Egyptians were highly heterogeneous. Moreover, both IVS10-11 G>A and R261Q showed previously unreported VNTR patterns. In conclusion, the study of PAH VNTR allele patterns among normal and PKU-affected Egyptian subjects has confirmed the high heterogeneity of the normal Egyptian population as well as the PKU patients

Molecular analysis of androgen resistance syndromes in Egyptian patients

This study aimed to examine AR and 5 alpha-reductase 2 [5 alpha R2] gene mutations among a sample of such cases as a first step towards instituting a screening program. Five families with a typical hormonal profile of 5 alpha RD were screened for major deletions of exons 3-5 of the 5 alpha R2 gene using polymerase chain reaction [PCR] and electrophoresis. Consequently, screening for point mutations was carried out using single strand conformational polymorphism [SS CP] analysis, followed by nucleotide sequencing. Likewise, seven patients with androgen insensitivity syndrome [AIS] were subjected to molecular analysis of AR exons B-H along the same scheme, except for the use of denaturing gradient gel electrophoresis [DGGE] for screening point mutations. The study showed the absence of major deletions in either gene. One family had abnormal electrophoretic mobility on SSCP of exon 5 of the 5 alpha R2 gene resulting from a point mutation of C to T substitution at codon 246. Another family showing retarded mobility on DGGE had a point mutation of G to A substitution at codon 889 of the AR gene. The study revealed two mutations that were previously reported in other geographically distinct populations inferring the possibility of the presence of mutational host spots in the genes