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Expression of NANOG, but not POU5F1, points to the stem cell potential of primitive germ cells in neonatal pig testis

S Goel, Lab. of Reproductive Biology, Kyoto University, Kyoto, 0081-75-, Japan
M Fujihara, Lab. of Reproductive Biology, Kyoto University, Kyoto, Japan
N Minami, Lab. of Reproductive Biology, Kyoto University, Kyoto, Japan
M Yamada, Kyoto, Japan
H Imai, Kyoto, Japan

Correspondence: Sandeep Goel, Email: sandeep.ccmb{at}gmail.com

Abstract

Gonocytes are primitive germ cells that are present in the neonatal testis and that are committed to male germline development. Gonocytes differentiate to spermatogonia, which establish and maintain spermatogenesis in the postnatal testis. However, it is unknown whether large animal species have pluripotency-specific proteins in the testis. Nanog and Pou5f1 (Oct3/4) have been identified as transcription factors essential for maintaining pluripotency of embryonic stem (ES) cells in mice. Here we show that NANOG protein was expressed in the germ cells of neonatal pig testes, but was progressively lost with age. NANOG was expressed in most of the lectin Dolichos biflorus agglutinin (DBA)- and ZBTB16-positive gonocytes, which are known gonocyte-specific markers in pigs. NANOG was also expressed in Sertoli and interstitial cells of neonatal testes. Interestingly, POU5F1 expression was not detected at either the transcript or protein level in neonatal pig testis. In the prepubertal testis, NANOG and POU5F1 proteins were primarily detected in differentiated germ cells such as spermatocytes and spermatids and rarely in undifferentiated spermatogonia. By using a testis transplantation assay, we found that germ cells from 2- to 4-day-old pigs could colonize and proliferate in the recipient mice testes, suggesting that primitive germ cells from neonatal pig testes have stem cell potential.