Topic E4 Flashcards Preview

BMS 2021 > Topic E4 > Flashcards

Flashcards in Topic E4 Deck (12):
1

What is sex determination?

- The earliest developmental event that establishes sex (male or female development)
- Results in differentiation of embryonic gonads into either testes or ovaries
- If testosterone is made by the testes male genitalia will form (female is default)

2

What is the origin of embryonic gonads?

- The intermediate mesoderm which gives rise to the kidneys and the embryonic gonads which develop on the surface of the embryonic kidney (mesonephros)

3

What are the homologous female gonad cell types for these males cells:
1. Sertoli cells
2. Leydig cells

1. Granulosa cells (supporting cells)
2. Theca cells (interstitial steroid hormone producing cells)

4

What is the first cell type to differentiate in the developing testis?

Sertoli cell

5

What is the critical testis determining factor?

- The TDF is the SRY (sex determining region of the Y) gene carried on the Y chromosome. Its presence in the genotype causes testis development.
- The SRY gene encodes a transcription factor with a DNA binding domain called the HMG box.

6

What other gene does SRY activate?

- SRY activates SOX9

7

What are SOX9 genes?

- Encodes a transcriptional activator
- Activated by the SRY gene
- A pleiotropic gene: has more than one function; required for testicular development and for chondrogenesis
- SOX 9 negatively feedacs to SRY; in SOX9 null mice SRY expression is maintained

8

How does SOX9 lead to testis development?

- It activates male specific genes during testis development such as FGF9

9

What is the male gonadal activation factor pathway:

- SRY gene present in genome --> activation of SOX9 --> SOX 9 negatively inhibits SRY action --> SOX9 activates FGF9 and other male pathway genes --> FGF9 positively feedbacks to SOX9

10

Is there a master gene on the X chromosome governing ovary development the same way SRY on the Y chromosome governs testis development?

- No; there are 2 key autosomal genes instead: R-spondin-1 and Wnt4

11

How do R-SPO1 and Wnt4 cause ovary development?

- R-SPO1 stabilised the beta-catenin pathway (activated by Wnt -> LRP + Fz receptor). RSPO-1 is only expressed in female embryonic gonads and induces Wnt4 expression.
- Wnt4 also upregulates the beta-catenin pathway.
- Wnt4 suppresses the male gonadal pathway

12

Which are the corresponding antagonistic female gonadal development signals for these male gonadal signals:
1. Sox9 and FGF9

1. R-SPO1 and Wnt4