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Testis; |
Laboratories of Anatomy3 and Experimental Animal Sciences,4 Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
Department of Veterinary Radiology,5 School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, 069-8501 Japan
ABSTRACT
Although mammals produce either sperm or eggs depending on their sex, we found oocytes in the testes of newborn MRL/MpJ male mice. In the present study, we report the morphological characteristics of testicular oocytes, the postnatal change of oocyte number per testis, and the expression of a few oocyte-specific genes in the testes of MRL/MpJ mice. The testicular oocytes had a diameter of 50–70 µm and were surrounded by zonae pellucidae, which were observed between oocytes and follicular epithelial cells. Ultrastructurally, the testicular oocytes contained numerous microvilli and cortical granules, receiving cytoplasmic projections from follicular epithelial cells. The testicular oocytes appeared as early as at birth, and the largest number was found on Day 14. The testicular oocytes were detected in only MRL strains and B6MRLF1, but not in C57BL/6, C3H/He, BALB/c, DBA/2, A/J, and MRLB6F1. The expression of the oocyte-specific genes Zp1, Zp2, Zp3, and Omt2a was detected in testes from MRL/MpJ mice. These results suggest that newborn male MRL/MpJ mice with XY chromosomes can produce oocytes in their testes and that one of the genes causing this exists on the Y chromosome.
follicular development, meiosis, mouse, MRL/MpJ, oocyte development, ovary, sex differentiation, testicular oocyte, testis
1Supported by grants from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (19380162) and the Novartis Foundation (Japan) for the Promotion of Science.
Correspondence: 2Yasuhiro Kon, Laboratory of Anatomy, Graduate School of Veterinary Medicine, Hokkaido University, Kita 18 Nishi9, Kita-ku, Sapporo 060-0818, Japan. FAX: 81 11 706 5189; e-mail: y-kon{at}vetmed.hokudai.ac.jp
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