C. Mori et al., UNIQUE HEXOKINASE MESSENGER-RIBONUCLEIC-ACID LACKING THE PORIN-BINDING DOMAIN ARE DEVELOPMENTALLY EXPRESSED IN MOUSE SPERMATOGENIC CELLS, Biology of reproduction, 49(2), 1993, pp. 191-203
We have identified cDNAs representing three hexokinase mRNAs (Hk1-sa,
Hk1-sb, Hk1-sc) by screening mouse spermatogenic cell cDNA libraries w
ith a mouse hepatoma cell line hexokinase (Hk1) cDNA [Arora KY, Fanciu
lli M, Pederson PL. J Biol Chem 1990; 265:6481-6488]. Although all thr
ee cDNAs show 99% identity to the somatic Hk1 cDNA sequence throughout
most of their coding region, they differ from this sequence at the 5'
end. They contain a common spermatogenic cell-specific sequence and a
sequence unique to each cDNA immediately 5' to the common domain. How
ever, they lack the porin-binding domain (PBD) present in this region
of Hk1, used for binding to a pore-forming protein in the outer mitoch
ondrial membrane. These observations appear to support a model propose
d by others for hexokinase gene evolution in mammals. In addition, we
found that Hk1-sb has an internal sequence that is not present in Hk1,
Hk1-sa, or Hk1-sc. Moreover, Hk1-sa and Hk1-sb transcripts are develo
pmentally expressed in mouse spermatogenic cells. Hk1-sa mRNA is first
expressed during meiosis and continues to be present in postmeiotic g
erm cells, while the more abundant Hk1-sb mRNA is detected only in pos
tmeiotic germ cells. These and other findings suggest that enzymes enc
oded by Hk1-sa, Hk1-sb, and Hk1-sc are present only in spermatogenic c
ells.