Da. Obrien et al., EXPRESSION OF MANNOSE 6-PHOSPHATE RECEPTOR MESSENGER RIBONUCLEIC-ACIDS IN MOUSE SPERMATOGENIC AND SERTOLI CELLS, Biology of reproduction, 50(2), 1994, pp. 429-435
Spermatogenic and sertoli cells isolated from the mouse synthesize dif
ferent proportions of the two mannose 6-phosphate receptors (MPR) duri
ng overnight culture periods (O'Brien et al., Endocrinology 1989; 125:
2973). To determine the relative expression of MPR mRNAs in these cell
s, poly(A)(+) RNAs were examined by Northern blot analysis using cDNA
probes specific for the cation-independent (CI) and cation-dependent (
CD) MPRs. A single CI-MPR transcript, similar to 10 kb in size, was pr
esent in all tissues and cell types examined. Like the CI-MPR protein,
this transcript was more abundant in Sertoli cells than in spermatoge
nic cells isolated from adult testes. The CD-MPR is the predominant MP
R synthesized by pachytene spermatocytes or round spermatids. Multiple
CD-MPR transcripts were detected in these cells, including a 2.4-kb C
D-MPR mRNA that was indistinguishable from CD-MPR transcripts in somat
ic tissues and Sertoli cells. Smaller CD-MPR mRNAs of similar to 1.4 a
nd 1.6 kb were prominent in pachytene spermatocytes and round spermati
ds, respectively, but were faint or undetectable in somatic tissues. T
hese smaller CD-MPR mRNAs did not hybridize with an 0.9-kb restriction
fragment derived from the CD-MPR 3' untranslated region (UTR), sugges
ting that alternate polyadenylation signals are used to produce multip
le CD-MPR transcripts in spermatogenic cells. When poly(A) tracts were
selectively removed from germ cell RNAs by ribonuclease H treatment,
identical 1.3-kb CD-MPR mRNAs were detected in pachytene spermatocytes
and round spermatids, indicating that the size difference between the
1.4- and 1.6-kb transcripts is due to variations in poly(A) tail leng
th. These alterations in the 3' UTR of the CD-MPR transcripts may affe
ct mRNA stability or translation during spermatogenesis.