Mice lacking FABP9/PERF15 develop sperm head abnormalities but are fertile

Abstract

The male germ cell-specific fatty acid binding protein 9 (FABP9/PERF15) is the major component of the murine sperm perforatorium and perinuclear theca. Based on its cytoskeletal association and sequence homology to myelin P2 (FABP8), it has been suggested that FABP9 tethers sperm membranes to the underlying cytoskeleton. Furthermore, its upregulation in apoptotic testicular germ cells and its increased phosphorylation status during capacitation suggested multiple important functions for FABP9. Therefore, we investigated specific functions for FABP9 by means of targeted gene disruption in mice. FABP9−/− mice were viable and fertile. Phenotypic analysis showed that FABP9−/− mice had significant increases in sperm head abnormalities (~8% greater than their WT cohorts); in particular, we observed the reduction or absence of the characteristic structural element known as the “ventral spur” in ~10% of FABP9−/− sperm. However, deficiency of FABP9 neither affected membrane tethering to the perinuclear theca nor the fatty acid composition of sperm. Moreover, epididymal sperm numbers were not affected in FABP9−/− mice. Therefore, we conclude that FABP9 plays only a minor role in providing the murine sperm head its characteristic shape and is not absolutely required for spermatogenesis or sperm function.

Cell-type-specific regulation of genes involved in testicular lipid metabolism: fatty acid-binding proteins, diacylglycerol acyltransferases, and perilipin 2

“…The fact that both increase in ascending order from PS to RS, from these cells to ES, and from these cells to RB explains why Fabp9 mRNA and protein accumulate during postnatal maturation in the testis. The presence of FABP9 protein at the latest stages of spermatid differentiation agrees with previous observations using immunohistochemistry in testis sections (Korley et al 1997, Selvaraj et al 2010. Our results detecting this protein in isolated ES and RB agree with the presence of this protein in mouse spermatozoa (Korley et al 1997).…”

“…3). In western blots, FABP9 was detected as a single band of 15 kDa, in agreement with previous work in adult mice (Selvaraj et al 2010). The protein was undetectable at P6, first appearing at around P18, i.e.…”

“…Further studies are still needed to establish the nature of the hydrophobic ligands of FABP9 and clarify its role in spermatogenesis. Intriguingly, mice lacking Fabp9 are viable and fertile, and the total lipid fatty acid profile of their spermatozoa is not apparently affected (Selvaraj et al 2010). It is then possible that the deficiency in FABP9 could be compensated by overexpression of Fabp12 in the germ cells of Fabp9-null mice, thereby enabling spermatogenesis to continue.…”

“…The predominant FABP in testis is widely accepted to be FABP9 (Kido & Namiki 2000, Selvaraj et al 2010, although other members of this family have also been reported, such as FABP3 (Watanabe et al 1991), FABP5 (Kingma et al 1998), and more recently FABP12 (Liu et al 2008, Yamamoto et al 2009). However, no studies are available comparing on the same basis the expression of different FABPs at definite periods of testis development and correlating this with their relative abundances, in particular testicular cell types.…”

Thiol changes during epididymal maturation: a link to flagellar angulation in mouse spermatozoa?

“…The rabbit polyclonal antibody against the perforatorium was successfully used for immunoblotting, as described below, but did not show specific staining by indirect immunofluorescence. Instead, we used a newly created rabbit polyclonal antibody for mouse FABP9, which was a gift from Dr. Alex Travis, for indirect immunofluorescence (Selvaraj et al ., ). An antibody for α‐tubulin (T5168; Sigma‐Aldrich, Saint Louis, MO, USA) was used as an internal control for immunoblotting to compare protein abundance between wild‐type and Adcy10 ‐null mice.…”