Prader-Willi syndrome

 Welcome back! This week we will be focussing on the genetics of Prader-Willi Syndrome. 


(Credit: Impactlab)

Prader-Willi syndrome is a rare epigenetic condition that causes learning difficulties, restricted growth, behavioural challenges, excessive appetite, and weakened muscles. In the early stages of life, the syndrome manifests as global developmental delay, and characteristic facial features as shown in the image below. 

(Credit: clingenetic)

Epigenetics influences which genes are turned on and off and when (gene expression). It involves adding a specific chemical group (methyl group) to the DNA, which silences or reduces gene expression. This process is essential as not all types of cells need the same genes activated due to their different roles. As said in previous posts, we inherit two copies of each gene - one maternal and one paternal. In some genes, one of the copies may be epigenetically silenced. This imprinting is unique among individuals, with roughly 1% of genes imprinted. 

(Credit: Biorender)

Prader-Willi syndrome is caused by the silencing of paternally expressed genes on chromosome 15 (15q 11-13). These genes that are normally expressed are silenced due to methylation, causing large deletions to the paternal chromosome. But occasionally, it can be inherited via maternal uniparental disomy; this is when an individual acquires two chromosomes 15 from the mother rather than one from each parent. In this case, the paternal chromosome 15 is missing, and therefore the individual will present with Prader-Willi syndrome. 


(Credit: Biorender)

The genes missing in Prader-Willi syndrome include SNRPN and NDN. The absence of SNRPN contributes to neurological and developmental impairments due to its importance in translating microRNA into proteins. NDN, on the other hand, encodes for a protein known as niacin, which is important for neuronal growth and regulating cell development. When absent, it will cause developmental and cognitive impairments. 

These clinical manifestations of Prader-Willi can limit their life expectancy, but after diagnosis, treatment can be used and is based on each individuals symptoms and complications. 

Thank you for tuning in to this weeks blog! Next, we are learning about Cystic fibrosis, how it is inherited, and how it affects those with the condition. 

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