Change of cyclin D2 mRNA expression during murine testis development detected by fragmented cDNA subtraction method

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Abstract
Using subtractive hybridization and polymerase chain reaction, we developed a differential cloning system, the fragmented cDNA subtraction method, that requires only small amounts of materials. The cloning system was used to isolate several cDNA fragments expressed more abundantly in the premeiotic day 3 post‐natal mouse testis than in the adult mouse testis. The isolated cDNA fragments included cDNA encoding the murine cyclin D2. Northern blot and in situ hybridization analyses revealed that, during testis development, cyclin D2 expression was most abundant in the neonatal proliferating Sertoli cells. Those type A spermatogonia that were thought to divide mitotically also expressed cyclin D2 mRNA. Other spermatogenic cells, such as mitotically arrested gonocytes in neonatal testis and meiotically dividing germ cells in adult testis as well as adult Sertoli cells, were negative for the cyclin D2 signal. Adult W/Wv mutant mice lacking germ cells expressed cyclin D2 mRNA in terminally differentiated Sertoli cells. Elimination of germ cells other than the undifferentiated type A spermatogonia by treating wild‐type mice with an anti‐c‐kit monoclonal antibody did not result in the expression of cyclin D2 in Sertoli cells. These results demonstrate that there are lineage‐ and developmental‐specific expression patterns of cyclin D2 mRNA during mouse testis development. At the same time, it is suggested that primitive type A spermatogonia affect the cyclin D2 expression of Sertoli cells.