Question

Retinitis pigmentosa is a genetic disease that causes the breakdown and loss of retinal cells. Retinitis pigmentosa often starts with decreased night vision and will progress to blindness as retinal cells die.

Several genes have been linked to Retinitis pigmentosa, one of which is GADD. Mice lacking GADD (these mice were experimentally created so that the GADD region of the genome was deleted) have increased expression of non-retinal genes in retinal cells. In other words, in these mutant mice, genes that are not normally expressed in the retina are expressed.

Crx is a key retinal transcription factor. Crx binds regulatory elements called CBRs (Crx-binding regions). GADD has two CBRs, one immediately proximal to the transcription start site (TSS), and one a few hundred base pairs downstream of the TSS.

If you created a mouse where you had removed the CBR regions in the GADD gene (homozygous deletion mutant) would you expect the level of GADD transcription to increase or decrease (relative to wildtype/normal)? Would GADD be the only gene affected by this deletion? Explain your answer.

Answer 1

- If you created a mouse where you had removed the CBR regions in the GADD gene (homozygous deletion mutant) would you expect the level of GADD transcription to increase or decrease (relative to wildtype/normal)?

We deleted the binding regions for the transcription factor, this means even though the transcription factor is present it won't be able to attach and induce transcription of GADD, this mouse will have a decreased transcription activity for GADD compared to wildtype

- Would GADD be the only gene affected by this deletion? Explain your answer.

Yes, it will be the only one, because we did not knocked out the transcription factor but only the binding regions (CBRs) in this specific gene. All the other genes wth CBR still have they CBR and the transcription factor is normally functioning