A Whole-Genome Sequencing Study Implicates GRAMD1B in Multiple Sclerosis Susceptibility.

Area of Science:

• Genetics
• Neuroimmunology
• Rare genetic variants

Background:

• Common genetic variants' role in multiple sclerosis (MS) is well-established through genome-wide association studies.
• The contribution of rare genetic variants to MS susceptibility remains largely unknown.
• Investigating rare variants is crucial for a comprehensive understanding of MS genetic architecture.

Purpose of the Study:

• To identify rare genetic variants contributing to multiple sclerosis (MS) susceptibility.
• To investigate the role of the GRAMD1B gene in MS pathophysiology.
• To explore the expression and function of GRAMD1B in the central nervous system (CNS) and immune cells.

Main Methods:

• Whole-genome sequencing was performed on a consanguineous Italian family with multiple affected individuals.
• The GRAMD1B gene was sequenced in additional familial MS cases and healthy controls.
• Functional studies assessed GRAMD1B expression in CNS and peripheral cells and its regulation by inflammatory stimuli.

Main Results:

• A novel missense variant (c.1801T > C) in GRAMD1B was identified in MS cases within a linkage peak.
• Additional rare GRAMD1B variants, including missense and splice-site mutations, were found in familial MS cases.
• GRAMD1B is expressed in neurons, astrocytes, microglia, monocytes, and macrophages; its expression is downregulated in active MS lesions and by inflammatory stimuli.

Conclusions:

• Rare variants in the GRAMD1B gene represent potential risk factors for multiple sclerosis.
• GRAMD1B downregulation in MS lesions and inflammatory conditions suggests a role in disease pathogenesis.
• Further research into GRAMD1B's function in the CNS and immune system is warranted for understanding MS.