Abstract
A recently reported deletion of about 40 Mb in length between 6.12/6.57 and 46.73/47.31 Mb on the Y chromosome long arm of the C57BL/6JBomTac inbred strain made us closely examine the strain’s breeding history and reproductive characteristics. We verified that the two copies of Rbm31y that are present inside the putative deletion were indeed deleted. This inbred strain presents an expected litter size for a C57BL/6 substrain. In vitro fertilization (IVF) efficiency and breeding efficiencies are comparable to those of the C57BL/6NTac substrain; however, the male/female sex ratio in the C57BL/6JBomTac is mildly skewed towards females. There is an increase in the percentage of sperm shape abnormalities found in C57BL/6JBomTac (35%) versus C57BL/6NTac (11%). The most frequent type of sperm abnormality observed is bent heads (19%). Additionally, there is deregulation of several transcripts expressed in the testes. We determined that this mutation arose in the C57BL/6JBomTac Foundation Colony in 2008, and it was completely fixed in the colony by 2009.
Highlights
The Y chromosome in mammals is quite unique; it is the smallest of the chromosomes and is found only in males
The rest of the Yq chromosome is the non-pairing Yq region (NPYq) or male-specific Y chromosome (MSY) region that is thought to be involved in spermatogenesis and fertility (Burgoyne et al 1992; Burgoyne 1998)
We verify a deletion in the Y chromosome of C57BL/6JBomTac mice, and we evaluate the effects of this deletion on the reproductive characteristics of this inbred strain
Summary
The Y chromosome in mammals is quite unique; it is the smallest of the chromosomes and is found only in males. It corroborated previous studies that showed several MSY genes present in multiple copies in the order of hundreds (Conway et al 1994) and other studies that showed many of these genes to be amplified en bloc and transcribed bidirectionally (Ellis et al 2007). These studies showed that these genes are mostly expressed in the testes (Toure et al 2005; Cocquet et al 2009; Ellis et al 2011). The mouse sequencing project provided the detailed architecture of the ampliconic 86.4 Mb of MSY sequence which consists of a 0.5 Mb unit amplified 200 times (Soh et al 2014)
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