The present invention provides a novel myomegalin isoform—myomegalin variant 8 (MMG8). The myomegalin variant 8 regulates microtubule organization at the Golgi apparatus, protein modification, secretion and trafficking, and cell proliferation. The present invention also provides nucleic acid molecules encoding the myomegalin isoforms, and vectors and host cells containing the nucleic acid molecules. Also provided are fusion constructs comprising the myomegalin isoform and antibodies that bind specifically to the myomegalin isoforms of the present invention. The present invention further provides uses of the myomegalin isoform as a diagnostic biomarker and as a target for screening for therapeutics for diseases such as cancer, diabetes, and lysosomal storage diseases.
