The human calcitonin receptor (CTR) is a transmembrane peptide with dual action 
as a receptor for the hormone calcitonin and as an extracellular calcium sensor. 
Therefore, CTR dysfunction could lead to disorders of calcium metabolism 
associated with hypercalcemia, such as the Williams syndrome (WS). WS is a 
developmental disorder caused by a deletion at chromosome 7q11.23 that includes 
the elastin locus (ELN). We have mapped the CTR gene (CALCR) to chromosome band 
7q21.3 by polymerase chain reaction and single-strand conformation analysis of 
somatic cell hybrids as well as fluorescence in situ hybridization (FISH) to 
metaphase chromosome spreads. Two-color FISH cohybridizing CTR and ELN probes 
confirmed that CALCR maps telomeric to ELN. Subsequent analysis of chromosome 
spreads from four WS patients revealed deletion of the ELN locus in all of them 
and normal hybridization of CTR probes to both chromosome 7 homologues, 
indicating that CALCR lies outside the deleted region.