Microtubules (MTs) are filamentous structures found throughout the cytoplasm of eukaryotic cells. They are polymers of tubulin that are involved in maintaining the structural integrity and plasticity of cells as well as the internal structures of cilia and flagella. Microtubules are also essential in several key cellular processes such as cell division and intracellular transport.
Proteins that accumulate at the ends of growing microtubules, known as MT plus end–tracking proteins, play an important role in regulating the dynamics and organization of the organelle. The SLAIN2 gene encodes one such MT plus end–tracking protein. This protein is targeted to microtubule tips by interacting with End-Binding proteins through its C-terminal domain. It is involved in cytoplasmic microtubule organization and nucleation. Through its N-terminal domain, it binds with the polymerase ch-TOG, recruiting it to the microtubule plus ends and thus ensuring microtubule elongation.
The SLAIN2 gene is located on the short arm of chromosome 4. It spans a length of 84.8 kb of DNA and its coding sequence is spread across 9 exons. The gene encodes a 62.5 kDa protein product comprised of 581 amino acids. SLAIN2 is widely expressed in the human body with high levels seen in the liver, testis and ovary.
Monies et al. (2017) assessed the genomic landscape of Saudi Arabia based on the findings of 1000 diagnostic panels and exomes. One patient, a 1-year-old female, presented with microcephaly, learning disability, developmental regression, severe hypotonia, infantile spasm seizures, delayed myelination and severe epileptic encephalopathy. Whole exome sequencing helped identify a homozygous mutation (c.938C>T, p.T313I) in exon 5 of the patient’s SLAIN2 gene. This gene mutation was considered a candidate for pathogenicity as it was a novel variant predicted to be deleterious; and the gene had an established role in neuronal development. Also, the gene had a pLI score of 0.88 indicating that it was highly likely to be intolerant of loss-of-function mutations. The authors noted the need for independent confirmation of this association.