Microcephaly

• Context (TH): Recent research by the Maternity and Child Health Care Hospital of Nantong University, China, have confirmed the role of the SASS6 gene in microcephaly.
• Findings: If one copy of the SASS6 gene is non-functional, the other retains some function. If both copies are non-functional, the embryo dies before becoming a foetus.

Microcephaly

Credit: MCH hospital

• It is a condition in which a baby’s head is much smaller than normal.
• Symptoms: Small brain, poor motor function & speech, abnormal facial features, intellectual disability.
• Why it happens?: During the peak phase of brain development in the embryo, cells that become neurons fail to divide normally.
• Possible Causes
  • Infections during pregnancy: Toxoplasmosis (caused by a parasite found in undercooked meat), campylobacter pylori, rubella, herpes, syphilis, cytomegalovirus, HIV and Zika Virus.
  • Exposure to toxic chemicals like arsenic and mercury, alcohol, radiation and smoking.
  • Genetic abnormalities such as Down syndrome.
  • Severe malnutrition during fetal life.
• Related Gene: The SASS6 gene and its variants have been linked to microcephaly since 2014.
• Diagnosis: Can be diagnosed before birth using fetal ultrasound and MRI.

About the SASS6 gene

• In 2004, researchers found the SASS6 gene in the roundworm Caenorhabditis elegans. These genes contain instructions for cells to make structures called centrioles.
• It encodes a protein with 657 amino acids. This protein assembles new centrioles during cell division. The protein made by this gene exists across animals.
• An individual with a slightly defective SASS6 gene can survive to birth and adulthood. However, they suffer serious brain and head deficits and intellectual disability.
• Different cell types tolerate deficits in centriole composition and function differently. Cells destined to become neurons are the least tolerant of imperfect centrioles.