Testis-specific expression of a functional retroposon encoding glucose-6-phosphate dehydrogenase in the mouse.
The X-chromosomal gene glucose-6-phosphate dehydrogenase (G6pd) is known to be expressed in most cell types of mammalian species. In the mouse, we have detected a novel gene, designated G6pd-2, encoding a G6PD isoenzyme. G6pd-2 does not contain introns and appears to represent a retroposed gene. This gene is uniquely transcribed in postmeiotic spermatogenic cells in which the X-encoded G6pd gene is not transcribed. Expression of the G6pd-2 sequence in a bacterial system showed that the encoded product is an active enzyme. Zymogramic analysis demonstrated that recombinant G6PD-2, but not recombinant G6PD-1 (the X-chromosome-encoded G6PD), formed tetramers under reducing conditions. Under the same conditions, G6PD tetramers were also found in extracts of spermatids and spermatozoa, indicating the presence of G6pd-2-encoded isoenzyme in these cell types. G6pd-2 is one of the very few known expressed retroposons encoding a functional protein, and the presence of this gene is probably related to X chromosome inactivation during spermatogenesis.
Hendriksen
P J
PJ
Department of Endocrinology and Reproduction, Faculty of Medicine and Health Sciences, Erasmus University, Rotterdam, The Netherlands.
Hoogerbrugge
J W
JW
Baarends
W M
WM
de Boer
P
P
Vreeburg
J T
JT
Vos
E A
EA
van der Lende
T
T
Grootegoed
J A
JA
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004303:Dosage Compensation, Genetic; D015870:Gene Expression; D005954:Glucosephosphate Dehydrogenase / Q000235:genetics*; D007527:Isoenzymes / Q000235:genetics; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D010802:Phylogeny; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D018626:Retroelements; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013091:Spermatogenesis / Q000235:genetics; D013737:Testis / Q000201:enzymology*; D014018:Tissue Distribution; D014960:X Chromosome / Q000235:genetics
D017931:DNA Primers; D007527:Isoenzymes; D012333:RNA, Messenger; D018626:Retroelements; D004247:DNA; D005954:Glucosephosphate Dehydrogenase