The present invention provides an isolated polypeptide exhibiting substantially the same amino acid sequence as JAGGED, or an active fragment thereof, provided that the polypeptide does not have the amino acid sequence of SEQ ID NO:5 or SEQ ID NO:6. The invention further provides an isolated nucleic acid molecule containing a nucleotide sequence encoding substantially the same amino acid sequence as JAGGED, or an active fragment thereof, provided that the nucleotide sequence does not encode the amino acid sequence of SEQ ID NO:5 or SEQ ID NO:6. Also provided herein is a method of inhibiting differentiation of hematopoietic progenitor cells by contacting the progenitor cells with an isolated JAGGED polypeptide, or active fragment thereof. The invention additionally provides a method of diagnosing Alagille Syndrome in an individual. The method consists of detecting an Alagille Syndrome disease-associated mutation linked to a JAGGED locus.
This invention was supported by grant numbers P30HD28834, P50HL54881, DK34431, DK51417, CA18221, HL36444, 1R01DK53104-01, DK02338-03 and 5P30HD288215 awarded by the National Institute of Health, USPHS Grant CA58207 and contract DE-AC-03-76SF00098 from the U.S. Department of Energy. The United States Government has certain rights in this invention.