Abstract
Spermatogenesis in mice is typically characterized by self-renewal and proliferation of spermatogonial stem cells (SSCs), which further give rise to mature sperm. The process of SSC self-renewal is regulated by number of genes. Oct-4 (POU family transcription factor) and Promyelocytic Leukemia Zinc Finger (Plzf) transcription factors are very well characterized and are known markers of undifferentiated spermatgonia. They are essential for self-renewal but their pattern of expression during the early events of spermatogenesis in mice has not been reported. Using real time PCR and Western blot we demonstrate marked increase in the expression of Oct-4 and Plzf in the testes of 10 days post partum (dpp) mice compared to 5 dpp both at the transcription and translation levels. The expression was found to be maximum in 10 dpp, declined in 20 dpp and was least in the testes of 35 dpp mice. However, our Immunohistochemistry (IHC) data showed the expression of OCT-4 & PLZF in the undifferentiated spermatogonia of 5, 10 & 20 dpp testes while in the testes of 35 dpp mice expression was seen in the undifferentiated as well as in differentiated spermatogonia. In conclusion, the present study reveals the expression pattern of Oct-4 and Plzf in the early stages of spermatogenesis of mice which sets the basis of spermatogenesis process in adults
Highlights
Spermatogenesis is a very complex and well orchestrated process involving differentiation of male germ cells to produce mature spermatozoa, and is divided into three distinct stages: the mitotic proliferation of spermatogonial stem cells (SSCs), meiotic division of spermatocytes, and spermiogenesis of haploid spermatids [1]
Relative testicular expression levels of Oct-4 and Promyelocytic Leukemia Zinc Finger (Plzf) quantitated by Q-PCR using Gapdh showed that the levels of Oct-4 increased (p < 0.001) by almost 3.34 fold (3.34 ± 0.85) (Figure 2a) while that of Plzf by 2.83 fold (2.83 ± 0.89) (p < 0.01) (Figure 2b) in the testes of 10 dpp mice when compared with 5 dpp testicular expression
At 0 dpp, gonocytes are in the quiescent stage, around 3 dpp gonocytes are converted into SSCs, on 5 dpp proliferation of SSCs starts, 10 dpp first appearance of spermatocytes, 20 dpp marked by appearance of spermatids and 35 dpp first appearance of spermatozoa marking the end of the first wave of spermatogenesis [20,21]
Summary
Spermatogenesis is a very complex and well orchestrated process involving differentiation of male germ cells to produce mature spermatozoa, and is divided into three distinct stages: the mitotic proliferation of SSCs, meiotic division of spermatocytes, and spermiogenesis of haploid spermatids [1]. Spermatozoa are continuously produced in large quantities throughout the life. The foundation of this process is led by self renewing SSCs. The continuity of spermatogenesis is dependent on the self renewing and differentiating capacities of SSCs. During spermatogenesis in adult mice, the stem cell activity resides in a small, primitive set of spermatogonia referred as the undifferentiated spermatogonia corresponding to Asingle, Apaired, and Aaligned (As, Apr and Aal) cells [2,3]. All types of spermatogonia (Asingle to B) are localized on the peripheral basement membrane
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