Sertoli cell in the context of Seminiferous tubule

Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. Sex differentiation is usually distinct from sex determination; sex determination is the designation of the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.

In many species, testicular or ovarian differentiation begins with the appearance of Sertoli cells in males and granulosa cells in females.

Sex-determining region Y protein (SRY), or testis-determining factor (TDF), is a DNA-binding protein (also known as gene-regulatory protein/transcription factor) encoded by the SRY gene that is responsible for the initiation of male sex determination in therian mammals (placentals and marsupials). SRY is an intronless sex-determining gene on the Y chromosome. Mutations in this gene lead to a range of disorders of sex development with varying effects on an individual's phenotype and genotype.

SRY is a member of the SOX (SRY-like box) gene family of DNA-binding proteins. When complexed with the steroidogenic factor 1 (SF-1) protein, SRY acts as a transcription factor that causes upregulation of other transcription factors, most importantly SOX9. Its expression causes the development of primary sex cords, which later develop into seminiferous tubules. These cords form in the central part of the yet-undifferentiated gonad, turning it into a testis. The now-induced Leydig cells of the testis then start secreting testosterone, while the Sertoli cells produce anti-Müllerian hormone. Effects of the SRY gene, which normally take place 6–8 weeks after fetus formation, inhibit the growth of female anatomical structure in males. The gene also contributes towards developing the secondary sexual characteristics of males.

A sustentacular cell is a type of cell primarily associated with structural support, they can be found in various tissues.

• Sustentacular cells of the olfactory epithelium (also called supporting cells or Sertoli cells) have been shown to be involved in the phagocytosis of dead neurons, odorant transformation and xenobiotic metabolism.
• One type of sustentacular cell is the Sertoli cell, in the testicle. It is located in the walls of the seminiferous tubules and supplies nutrients to sperm. They are responsible for the differentiation of spermatids, the maintenance of the blood-testis barrier, and the secretion of inhibin, androgen-binding protein and Müllerian-inhibiting factor.
• The organ of Corti in the inner ear and taste buds also contain sustentacular cells.
• Another type of sustentacular cell is found with glomus cells of the carotid and aortic bodies.
• About 40% of carcinoids have a scattering of sustentacular cells, which stain positive for S-100.