Context: Autosomal dominant neurohypophyseal diabetes insipidus (ADNDI) has been known as a rare disorder transmitted as an autosomal dominant trait, characterized by polyuria and polydipsia, and caused by deficient neurosecretion of arginine vasopressin precursor (AVP-NPII). We reported an ADNDI family with linkage to chromosome 20p13 but without mutations in the AVP-NPII gene.
Objective: The objective of this study was to identify the corresponding locus responsible for ADNDI in a family without AVP-NPII gene mutations.
Subjects and Methods: Two families with ADNDI were diagnosed by water deprivation test. The AVP-NPII gene was amplified by PCR and sequenced. A genomewide scan was performed in one family using 400 microsatellite markers covering 22 autosomes.
Results: A 3-bp deletion (1827-1829delAGG) of AVP-NPII gene was identified in the affected individuals in one family. Although no mutations could be detected in the coding, the promoter, and intronic regions of AVP-NPII gene in the other family, a maximum LOD score of 1.202999 (theta = 0.00) was obtained at marker D20S889 by genomewide scan, and a 7-cM interval on chromosome 20p13 was defined by fine mapping with markers D20S199-D20S849. Furthermore, the intragenic region that regulates AVP-NPII and oxytocin expression as an enhancer element and the UBCE7IP5 gene that participates in prohormone degradation were sequenced. No alterations could be detected either.
Conclusion: The corresponding locus responsible for ADNDI is possibly heterogeneous regarding the slightly different clinical features in these two families.
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