Divergent outcomes of intrachromosomal recombination on the human Y chromosome: male infertility and recurrent polymorphism

• Published in: Journal of medical genetics 2000-10, Vol.37 (10), p.752-758
• Main Authors: Blanco, Patricia, Shlumukova, Maria, Sargent, Carole A, Jobling, Mark A, Affara, Nabeel, Hurles, Matthew E
• Format: Article
• Language: English
• Subjects: AZFa; Biological and medical sciences; Chromosome Breakage - genetics; Chromosome Deletion; Chromosomes; Cloning, Molecular; Crossing Over, Genetic - genetics; Deoxyribonucleic acid; DNA; Endogenous Retroviruses - genetics; Evolution, Molecular; General aspects. Genetic counseling; Genes; Genetic testing; Genomes; Haplotypes; HERV; Humans; Infertility; Infertility, Male - genetics; Infertility, Male - pathology; Male; Medical genetics; Medical sciences; Mitochondrial DNA; Models, Genetic; Molecular Sequence Data; Mutation; Mutation - genetics; Original; Phylogeny; Polymerase Chain Reaction; Polymorphism, Genetic - genetics; Sequence Homology, Nucleic Acid; Sertoli Cells - metabolism; Sertoli Cells - pathology; Studies; Y chromosome; Y Chromosome - genetics
• ISSN: 0022-2593; 1468-6244; 1468-6244
• DOI: 10.1136/jmg.37.10.752

The Y chromosome provides a unique opportunity to study mutational processes within the human genome, decoupled from the confounding effects of interchromosomal recombination. It has been suggested that the increased density of certain dispersed repeats on the Y could account for the high frequency of causative microdeletions relative to single nucleotide mutations in infertile males. Previously we localised breakpoints of an AZFamicrodeletion close to two highly homologous complete human endogenous retroviral sequences (HERV), separated by 700 kb. Here we show, by sequencing across the breakpoint, that the microdeletion occurs in register within a highly homologous segment between the HERVs. Furthermore, we show that recurrent double crossovers have occurred between the HERVs, resulting in the loss of a 1.5 kb insertion from one HERV, an event underlying the first ever Y chromosomal polymorphism described, the 12f2 deletion. This event produces a substantially longer segment of absolute homology and as such may result in increased predisposition to further intrachromosomal recombination. Intrachromosomal crosstalk between these two HERV sequences can thus result in either homogenising sequence conversion or a microdeletion causing male infertility. This represents a major subclass ofAZFa deletions.