Differences of sperm motility in mitochondrial DNA haplogroup U sublineages.
Montiel-Sosa F, Ruiz-Pesini E, Enríquez JA, Marcuello A, Díez-Sánchez C, Montoya J, Wallace DC, López-Pérez MJ.
Departamento de Bioquímica, Biología Molecular y Celular, Universidad de Zaragoza, C/ Miguel Servet 177, 50013 Zaragoza, Spain.
We had previously shown that sperm from men harbouring haplogroup T mtDNAs swim less vigorously than those from haplogroup H. However, the biochemical basis of this motility was difficult to investigate because of the multiple mutations, the most important of which affected respiratory complex I for which there is no crystal structure. To more thoroughly study the relationship between mtDNA variation and differences in mitochondrial energy metabolism, we turned to the analysis of sperm baring haplogroup U mtDNAs. Haplogroup U is a monophyletic ancient and thus heterogeneous maternal lineage that is broadly distributed among European individuals. Several sublineages of haplogroup U were found to be associated with differences in sperm motility and vitality. These differences could be related to a highly conserved missense mutation in the mtDNA COIII gene (V91) and several equally conserved mutations in the cytochrome b (cytb) gene. Moreover, the lineages with the cytb mutations were substantially enriched in northern Europe, while those lacking these mutations were more prevalent in southern Europe. We suggest that some of these ancient conserved cytb missense mutations permitted our ancestors to adapt to cold by partially uncoupling mitochondrial oxidative phosphorylation (OXPHOS).
I’d like to see this repeated with Y chromosomes. But I’ve dug up another publication with more information along the same lines.
mtDNA Haplogroup Associated with Asthenozoospermia
On the basis of their observation that inhibitors of mitochondrial activity reduced sperm motility, Ruiz-Pesini et al. decided to investigate the potential genetic association between mtDNA variance and sperm motility. The authors used sperm samples from 545 donors (predominantly whites) and characterized the mtDNA into known haplogroups on the basis of polymorphic sites in the mtDNA (Richard et al. 1996; Torroni et al. 1996, 1997; Brown et al. 1997; Hofmann et al. 1997a, 1997b). They then grouped the sperm samples, on the basis of sperm motility, into three groups: nonasthenozoopermic (non-AP; 50% of progressive spermatozoa), moderately asthenozoospermic phenotype (MAP; 25% and <50% of progressive spermatozoa), and severely asthenozoospermic phenotype (SAP; <25% of progressive spermatozoa). They analyzed the percentage of the different haplogroups in each motility group. A significant overrepresentation of haplogroup H was found in the non-AP individuals (normal sperm motility), and a significant overrepresentation of haplogroup T was found in the MAP individuals (reduced sperm motility), even though both haplogroups belong to a population of white males. The authors also observed a significant difference between the maximum swimming distance for sperm from haplogroup H and that for sperm from haplogroup T, with the distance for sperm from haplogroup H being longer. These results established a correlation between mtDNA variation and sperm motility.
If mt DNA affect sperm quality, I’d be pretty surprised if the Y chromosome didn’t too.