Spermatogenesis

Biology and Clinical Implications

C. Yan Cheng, C. Yan Cheng

• Publisher: CRC Press
• Year: 2018
• ISBN:
  9780429949487
• Edition: 1
• Topic: Medicine
• Subtopic: Medical Theory, Practice & Reference

Senior investigators internationally have here collaborated to produce an international reference work. Each contributor provides critical and thought provoking concepts and ideas based on the latest developments in their field. The result is a must read and timely reference work for investigators who are interested in how spermatogenesis is currently understood and which are the most promising avenues for future research; an Introduction sets the context for the chapter and points out the relevance of the research for basic research scientists and clinicians.

1Golgi apparatus regulation of differentiationA case study for male germ cells of the rat testis

Louis Hermo, Regiana L. Oliveira, Charles E. Smith, Catherine E. Au, and John J. M. Bergeron

Introduction

The Golgi apparatus is found in each of the estimated more than 200 different cell types that make up the human body.1 Golgi apparatus structure visualized by standard thin sectioning techniques at the electron microscope (EM) level, which reached its apogee in the latter part of the last century, can identify solely and unambiguously any of the differentiated cell types in a given species. Remarkably, its structure is strictly conserved with the number and size of cisternae in Golgi stacks and overall size of the Golgi apparatus under strict control for each of the many differentiated cell types of a given organ of the human body. This conjecture has been illustrated here for the Golgi apparatus using the well-described differentiation of male germ cells in the adult rat testis.

Spermatogenesis: A discovery based on the Golgi apparatus

In the mid-1950s, detailed light microscope (LM) observations elucidated the complexity of the differentiation pathway of male germ cells in seminiferous tubules of the testis, a process referred to as spermatogenesis. The periodic acid Schiff (PAS) technique2 was the breakthrough that enabled both the steps of germ cell differentiation to be uncovered as well as the discovery of stem cells (Figure 1.1).

Figure 1.1Chemical ingredients for the Schiff reaction. (Reproduced with permission from Wako Chemicals USA.)

The PAS stain is specific to vicinyl hydroxyls and when applied to the testis reveals staining of the Golgi apparatus and Golgi derived acrosome of germ cells.3 The reaction due to carbohydrate modifications on glycoproteins is modulated by Golgi localized glycosyltransferases. This method provides a precise mapping of how germ cells associate with each other in cross sections of seminiferous tubules of the testis, as first described by Leblond and Clermont3 (Figure 1.2).

Figure 1.2Schematic drawings of portions of seminiferous tubules, each representing one of the 14 well-defined stages of the cycle of the seminiferous epithelium as revealed from PAS-hematoxylin stained preparations. Stages are represented by roman numerals. Spermatogonia: type A, intermediate (In) and B; InM and BM, mitosis of In and B spermatogonia; preleptotene (Pl), leptotene (L), zygotene (Z), pachytene (P), diplotene/diakinesis (Di) spermatocytes and secondary spermatocytes (II). IM and IIM, first and second meiotic divisions. Arabic numbers represent the 19 steps of differentiation of spermatids undergoing spermiogenesis. RB, residual body. (Reproduced with permission from American Physiological Society. Clermont, Y. Physiol Rev. 1972;52(1):198–236.)

In the seminiferous epithelium, germ cells at different steps of differentiation associate with each other to form specific cellular associations referred to as stages of the cycle of the seminiferous epithelium. The PAS method was the first test in defining the significance of the Golgi apparatus in understanding the differentiation process of any organ undergoing renewal. Even more important was the first identification of stem cells identified as a constantly replenished population undergoing ...