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9-SepA gene on chromosome 17q25 that encodes septin 9, a member of the septin family of nucleotide-binding proteins, which are required for cytokinesis, organisation of submembranous structures, neuronal polarity and vesicle trafficking. SEPT9 is a candidate for ovarian tumour suppressor gene.
SEPT9 mutations cause hereditary neuralgic amyotrophy (neuritis with brachial predilection). A translocation between SEPT9 and MLL on chromosome 11 results in acute myelomonocytic leukaemia.