The development of an embryo is a well-orchestrated string of processes, ensuring correct formation and positioning of vital organs of the growing organism. At the molecular level, these processes are controlled in a precise manner by switching on or off specific factors such as genes or proteins. Any errors in these processes could result in physical defects or disease in the newborn organism.

A team of scientists from the National University of Singapore (NUS) led by Assistant Professor Xue Shifeng from the Department of Biological Sciences has discovered a new way to interpret unsolved Mendelian diseases — diseases inherited from either parent due to gene mutations in the developing egg or sperm — through studying the inheritance of a protein known as SMCHD1 which is coded by the SMCHD1 gene. Mutations in the SMCHD1 gene can cause diseases such as facioscapulohumeral muscular dystrophy (FSHD) which is a muscle degenerative disorder, and Bosma arhinia microphthalmia syndrome (BAMS) which causes abnormalities of the nose and eyes.

The researchers found that SMCHD1 from mothers controls the expression of a group of genes in offspring, known as the HOX genes, which determines the position of body parts in an embryo along the axis from its head to tail. The researchers also found that the inactivation of SMCHD1 in female zebrafish results in alterations to HOX gene expression leading to skeletal defects in their offspring.

The study led by NUS researchers, in collaboration with A*STAR, Yale-NUS and Aix-Marseille University, was published in Nature Communicationson 23 June 2022.

Inheritance of mother’s genes and structural defects

In mammals, SMCHD1 plays a key role in X-inactivation in females, a process where one of the copies of the X chromosome is randomly selected and disabled. This makes it challenging to study the role of the SMCHD1 gene inherited from mothers because inactivating the SMCHD1 gene is lethal for female mammals.

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