Expansion of theHSFYgene family in pig lineages

Abstract

Amplified gene families on sex chromosomes can harbour genes with important biological functions, especially relating to fertility. The HSFY family has amplified on the Y chromosome of the domestic pig (Sus scrofa), in an apparently independent event to an HSFY expansion on the Y chromosome of cattle (Bos taurus). Although the biological functions of HSFY genes are poorly understood, they appear to be involved in gametogenesis in a number of mammalian species, and, in cattle, HSFY gene copy number correlates with levels of fertility.We have investigated the HSFY family in domestic pigs, and other suid species including warthogs, bushpigs, babirusas and peccaries. The domestic pig contains at least two amplified variants of HSFY, distinguished predominantly by presence or absence of a SINE within the intron. Both these variants are expressed in testis, and both are present in approximately 50 copies each in a single cluster on the short arm of the Y. The longer form has multiple nonsense mutations rendering it likely non-functional, but many of the shorter forms still have coding potential. Other suid species also have these two variants of HSFY, and estimates of copy number suggest the HSFY family may have amplified independently twice during suid evolution.Given the association of HSFY gene copy number with fertility in cattle, HSFY is likely to play an

Horse Y chromosome assembly displays unique evolutionary features and putative stallion fertility genes

“…1b and Supplementary Data 6 ). However, compared to the massive amplification of HSFY in pigs 14 , 26 and cattle 12 , or TSPY in cattle 12 and cats 13 , their copy numbers in eMSY were moderate. The equine X–Y ampliconic genes were expressed in adult testis and, except for UBA1Y , in male embryonic gonads (Supplementary Fig.…”

“…Alternatively, it may be that ETSTY7 copy number in donkey Y is too low for detection by FISH. Even though expansion of lineage-specific testis transcripts is a characteristic feature of all studied mammalian Y chromosomes 5 , 10 , 13 , 14 , 26 , ETSTY7 distribution in equids is unique with no analogy in other eutherians.…”

“…Of these, the multi-copy testis-specific HSFY is proposed as a candidate male-benefit gene in other eutherians. It belongs to critical azoospermia region (AZFb) in human MSY 43 , and is massively expanded in the MSY of pig 26 and cattle 12 . Furthermore, HSFY has a chicken orthologue that is predominantly expressed in testis 12 , suggesting that this is an ancient vertebrate male fertility gene, though HSFY biological functions remain currently enigmatic 26 .…”

The pig X and Y Chromosomes: structure, sequence, and evolution

“…2). These blocks are separated by a region containing highly amplified sequences including ∼100 copies of the HSFY gene family (Skinner et al 2015). Our final mapped sequence comprises seven contigs each in the distal and proximal blocks (Supplemental Fig.…”

“…The HSFY family: These genes are predominantly found in a block between the proximal and distal low-copy gene clusters and show evidence for recent amplification in the Sus lineage to ∼100 copies, with independent amplification in other suid species (Skinner et al 2015) and further independent amplification in cattle (Chang et al 2013). HSFY is expressed in pig testis and may have a role in spermatogenesis, though biological function remains to be established.…”