Morphological and quantitative analysis of spermatogonia in mouse testes using whole mounted seminiferous tubules. I. The normal testes

Abstract

The spermatogonial populations in ten normal adult mice were analyzed using whole mounted seminiferous tubules. The undifferentiated A spermatogonia as well as the six generations of differentiating spermatogonia were clearly identifiable on whole mounts. Description plus quantitation of these cell types revealed that they behaved in essentially the same manner as their counterparts in the rat. Single undifferentiated A cells were classified as type As stem cell spermatogonia. They were distributed throughout the seminiferous epithelium, and by periodic mitoses, maintained their stock and furnished cells which would eventually differentiate. Although initially resembling the As spermatogonia, the progeny which were destined to differentiate were classified as type Aal spermatogonia because they were linked by cytoplasmic bridges, and because they usually underwent one or more synchronous mitotic divisions to form short chains of aligned cells. Ultimately, division of Aal cells were no longer seen, and the cells appeared to gradually acquire the typical morphological characteristics of A1 spermatogonia; these continued to differentiate according to the well-established pattern. It was concluded that the cyclic production of cohorts of A1 cells in this manner would ensure a continual supply of spermatogonia for differentiation.

Gdnf signaling pathways within the mammalian spermatogonial stem cell niche

“…Morphologically, they are undifferentiated single cells that are not connected by intercellular bridges like the more advanced germ cells (Huckins, 1971;Oakberg, 1971;Dym and Fawcett, 1971;de Rooij and Russell, 2000). According to the model of Huckins and Oakberg (Huckins and Oakberg, 1978), SSCs renew themselves or differentiate into two daughter cells called Apaired spermatogonia (Figure 1). Apaired spermatogonia further divide to form chains of 4, 8 or 16 Aaligned spermatogonia.…”

Spermatogonial Stem Cell Self-Renewal Requires OCT4, a Factor Downregulated During Retinoic Acid-Induced Differentiation

“…Undifferentiated spermatogonia include single cells (A s ; single A-type spermatogonia), as well as interconnected pairs (A pr ; paired A-type spermatogonia) and chains of cells of up to 32 cells in length (A al ; aligned A-type spermatogonia) [1,2]. The transition from undifferentiated (A al ) to differentiated (A 1 ) spermatogonia is characterized by major changes in gene expression and a different nuclear staining morphology, which historically was the basis for distinguishing these cell types [3][4][5].…”

TEX14 is essential for intercellular bridges and fertility in male mice

“…Instead, the midbody intercellular bridge is altered both structurally and molecularly into a distinct, stable germ cell intercellular bridge that connects the daughter cells in a syncytium. More than 50 years of study have provided a detailed morphological and structural description of intercellular bridges and the resulting syncytium (6)(7)(8)(9)(10)(11)(12)(13). Intercellular bridges are produced by both mitotic (6,12) and meiotic (7,8) divisions and create large, 0.5-to 3-m connections linking the cytoplasm of generations of daughter cells.…”

“…More than 50 years of study have provided a detailed morphological and structural description of intercellular bridges and the resulting syncytium (6)(7)(8)(9)(10)(11)(12)(13). Intercellular bridges are produced by both mitotic (6,12) and meiotic (7,8) divisions and create large, 0.5-to 3-m connections linking the cytoplasm of generations of daughter cells. Because the intercellular bridges remain stable during development, germs cells sharing a common parent cell develop clonally in a syncytium (6)(7)(8)(9)(10)(11), which can contain hundreds of synchronously developing germ cells (12,13).…”