This family of proteins is found in eukaryotes. Proteins in this family are typically between 384 and 835 amino acids in length. Microcephalin is involved in determining the size of the brain in animals. It is a protein, which if expressed homozygously causes the organism to have the condition microcephaly. Organisms expressing the mutated form of this protein in a homozygous manner develop a condition called microcephaly - a drastically reduced brain mass and volume. Microcephalin is predicted to contain three BRCA1 C-terminal domains, the first of which is the probable microcephaly mutation site.