The spatio-temporal pattern of testis organogenesis in mammals - insights from the mole

Abstract

Some cellular events are crucial in testis organogenesis, including Sertoli and Leydig cell differentiation, mesonephric cell migration and testis cord formation. These processes are controlled by transcription factors, paracrine signalling and hormones. Using the mole species Talpa occidentalis as an alternative animal model, we report the expression patterns of nine genes during testis differentiation and analyse their implications in the above-mentioned cellular processes. We show that: 1) Sertoli cell differentiation occurs very early and precedes mesonephric cell migration, indicating that the latter is not needed for the endocrine cytodifferentiation of Sertoli cells; 2) the time of Leydig cell differentiation is consistent with the participation of PDGFR-α in promoting the migration and/or proliferation of Leydig cell precursors, and with that of WNT4 signalling in inhibiting Leydig cell differentiation and 3) the formation of the tunica albuginea involves intragonadal cell migration/movement. These results demonstrate that testicular organogenesis in the mole differs from that in the mouse in some particular aspects, thus providing evidence that the spatio-temporal pattern of testis development is not highly conserved during mammalian evolution.

Retinal development and function in a ‘blind’ mole

“…Developmental stages were determined according to Barrionuevo et al (2004b) and Carmona et al (2009).…”

Building the mammalian testis: origins, differentiation, and assembly of the component cell populations

“…Studies from various mammalian species have shown that the tunica albuginea forms early during fetal testis differentiation, shortly after the primitive testis cords (Waters and Trainer 1996;Karl and Capel 1998;Carmona et al 2009). The process involves the formation of a fibrous basement membrane just beneath the coelomic epithelium and is suggested to involve both cell movement and differentiation, as cells need to undergo changes in shape and location and are known to express migratory markers (Carmona et al 2009).…”

“…The process involves the formation of a fibrous basement membrane just beneath the coelomic epithelium and is suggested to involve both cell movement and differentiation, as cells need to undergo changes in shape and location and are known to express migratory markers (Carmona et al 2009). It is still unclear exactly what cells contribute to this membrane, and both the coelomic epithelium and testis interstitium have been proposed (Karl and Capel 1998;Carmona et al 2009). Also, as discussed, extragonadal cell migration contributes to key morphological events of early testis differentiation, but after the formation of the tunica albuginea, this cell migration ceases (Karl and Capel 1998).…”

Ovarian Organogenesis in Mammals: Mice Cannot Tell Us Everything

“…Hundreds of embryological studies have been performed afterwards, describing many different aspects of gonad embryology in most vertebrate taxa, including mammals, birds, reptiles, amphibians, and others. Current knowledge indicates that, apart from some differences between species in the spatio-temporal pattern of differentiation [Carmona et al, 2009a], testis development is a quite well-conserved process, whereas ovarian development is much more heterogeneous, with substantial differences between taxa, including those belonging to the same class. There is also controversy concerning the embryological origin of the different gonadal components and the general model of gonad development.…”

“…One day later (18 dpc), primary sex cords appear in the medullary region of both XX and XY gonads. Testicular differentiation begins this way in male embryos and proceeds normally in subsequent days [Barrionuevo et al, 2004;Carmona et al, 2009a]. Ovarian tissue, which develops very slowly in the female moles, derives from the cortical region where all primordial germ cells concentrate.…”