High frequencies of Non Allelic Homologous Recombination (NAHR) events at the AZF loci and male infertility risk in Indian men.

Deletions in the AZoospermia Factor (AZF) regions (spermatogenesis loci) on the human Y chromosome are reported as one of the most common causes of severe testiculopathy and spermatogenic defects leading to male infertility, yet not much data is available for Indian infertile men. Therefore, we screened for AZF region deletions in 973 infertile men consisting of 771 azoospermia, 105 oligozoospermia and 97 oligoteratozoospermia cases, along with 587 fertile normozoospermic men. The deletion screening was carried out using AZF-specific markers: STSs (Sequence Tagged Sites), SNVs (Single Nucleotide Variations), PCR-RFLP (Polymerase Chain Reaction - Restriction Fragment Length Polymorphism) analysis of STS amplicons, DNA sequencing and Southern hybridization techniques. Our study revealed deletion events in a total of 29.4% of infertile Indian men. Of these, non-allelic homologous recombination (NAHR) events accounted for 25.8%, which included 3.5% AZFb deletions, 2.3% AZFbc deletions, 6.9% complete AZFc deletions, and 13.1% partial AZFc deletions. We observed 3.2% AZFa deletions and a rare long AZFabc region deletion in 0.5% azoospermic men. This study illustrates how the ethnicity, endogamy and long-time geographical isolation of Indian populations might have played a major role in the high frequencies of deletion events.

A novel androgen receptor mutation resulting in complete androgen insensitivity syndrome and bilateral Leydig cell hyperplasia.

Androgens drive male secondary sexual differentiation and maturation. Mutations in the androgen receptor (AR) gene cause a broad spectrum of abnormal phenotypes in humans, ranging from mild through partial to complete androgen insensitivity. We have analyzed the AR gene by using denaturing high-performance liquid chromatography (DHPLC) and direct sequencing and have studied gonads histologically in a familial case of complete androgen insensitivity syndrome. Sequence analysis of the AR gene showed a novel C2578T missense mutation, resulting in the replacement of a highly conserved leucine residue with phenylalanine (L859F) in ligand-binding domain of the receptor. The residue L859, located in helix 10 of the androgen receptor, plays a significant role in overall architecture of ligand-binding pocket. The mutation was absent from the father, normal brother of the patients, and 100 normal males recruited in this study as controls. The inheritance of the mutation in the family clearly shows that C2578T is the underlying mutation for the eventual phenotype in the patients. Histology of patient's gonads showed Leydig cell hyperplasia, with a few or no spermatogonium. It is thought that AR gene mutations result in hormonal imbalance, resulting in the high levels of luteinizing hormone (LH) and ultimately Leydig cell hyperplasia or tumor formation. In the present study, we have reported a rare familial case of Leydig cell hyperplasia despite consistently normal LH levels. The finding will help in giving counseling to this family and prevent the transmission of the mutated X chromosome to the coming generations.

Sperm mitochondrial mutations as a cause of low sperm motility.

We report the unique case of a 28-year-old man who, in spite of having a varicocele and a sperm concentration of 5 million/mL, of which 10% were motile and 20% had normal forms (oligoasthenoteratozoospermia [OAT]), was fertile. This was confirmed by paternity testing using 16 autosomal and 6 Y-chromosomal short tandem repeat (STR) loci. An analysis of mitochondrial genes that included cytochrome oxidase I (COI), cytochrome oxidase II (COII), adenosine triphosphate synthase6 (ATPase6), ATPase8, transfer ribonucleic acid (tRNA) serine I, tRNA lysine, and NADH dehydrogenase3 (ND3) revealed, for the first time, 9 missense and 27 silent mutations in the sperm's mitochondrial DNA (mtDNA) but not in the DNA from the blood cells. There was a 2-nucleotide deletion in the mitochondrial COII genes, introducing a stop codon, which might be responsible for low sperm motility.

Reconstructing the origin of Andaman Islanders.

The origin of the Andaman "Negrito" and Nicobar "Mongoloid" populations has been ambiguous. Our analyses of complete mitochondrial DNA sequences from Onges and Great Andaman populations revealed two deeply branching clades that share their most recent common ancestor in founder haplogroup M, with lineages spread among India, Africa, East Asia, New Guinea, and Australia. This distribution suggests that these two clades have likely survived in genetic isolation since the initial settlement of the islands during an out-of-Africa migration by anatomically modern humans. In contrast, Nicobarese sequences illustrate a close genetic relationship with populations from Southeast Asia.