Y chromosome haplogroup 26 associated with reduced sperm counts

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Human Molecular Genetics, 2001, Vol. 10, No. 18 1873-1877

Identification of a Y chromosome haplogroup associated with reduced sperm counts
C. Krausz1,2, L. Quintana-Murci1, E. Rajpert-De Meyts3, N. Jørgensen3, M.A. Jobling4, Z.H. Rosser4, N.E. Skakkebaek3 and K. McElreavey1,+
1Immunogénétique Humaine, INSERM E021, Institut Pasteur, Paris, France, 2Andrology Unit, University of Florence, Florence, Italy, 3University Department of Growth and Reproduction, Rigshospitalet, 9, Blegdamsvej, DK-2100, Copenhagen, Denmark and 4Department of Genetics, University of Leicester, Leicester, UK

In man, infertility is associated with microdeletions of specific regions of the long arm of the Y chromosome. This indicates that factors encoded by the Y chromosome are necessary for spermatogenesis. However, the majority of men with either idiopathic azoospermia or oligozoospermia have grossly intact Y chromosomes and the underlying causes of their infertility are unknown. We hypothesized that some of these individuals may carry other rearrangements or sequence variants on the non-recombining region of the Y chromosome that may be associated with reduced spermatogenesis. To test this hypothesis, we typed the Y chromosome in a group of Danish men with known sperm counts and compared the haplotype distribution with that of a group of unselected Danish males. We found that one class of Y chromosome, referred to as haplogroup 26+, was significantly overrepresented (27.9%; P < 0.001) in the group of men with either idiopathic oligozoospermia (defined as <20 x 106 sperm/ml) or azoospermia compared to the control Danish male population (4.6%). This study defines, for the first time, a class of Y chromosome that is at risk for infertility in a European population. This observation suggests that selection may be indeed active on the Y chromosome, at least in the Danish population, raising the possibility that it could alter the pattern of Y chromosome haplotype distribution in the general population.

+ To whom correspondence should be addressed. Tel: +33 1 45 68 89 20; Fax: +33 1 45 68 86 39; Email: kenmce@pasteur.fr