Methods and primers for diagnosing idiopathic congenital central hypoventilation syndrome

Abstract

The present invention provides assays and kits for diagnosing idiopathic congenital central hypoventilation syndrome. The present assays and kits focus on the second polyalanine repeat of the PHOX2b gene or gene product, which is normally 20 residues in length. A polyalanine repeat 25 to 33 residues in length is strongly correlated with idiopathic congenital central hypoventilation syndrome.

1 - 24 . (canceled) 
     
     
         25 . A method to determine a genotype of a human subject in terms of polyalanine repeat expansion mutations, wherein up to 33 alanine residues are detected in a biological sample by comparison with standards of predetermined alanine lengths, the method comprising:
 (a) determining whether only a normal 20 repeat is detectable, from which the genotype is inferred to be homozygous normal;   (b) determining whether both an allele with a normal 20 repeat and an allele with at least one polyalanine repeat expansion mutation are present, and wherein the ratios detected are consistent with standard values expected when all somatic cells have both alleles, from which the genotype is inferred to be heterozygous; and   (c) determining whether both an allele with a normal 20 repeat and an allele with at least one polyalanine repeat expansion mutation are present, but the ratio of the normal and mutated allele is indicative of mosacisim.   
     
     
         26 . The method of  claim 25 , wherein the polyalanine expansion mutation is detected by a polymerase chain reaction. 
     
     
         27 . The method of  claim 25 , wherein the polyalanine expansion mutation is detected by direct sequencing. 
     
     
         28 . The method of  claim 25 , wherein at least 95% of the human subjects with CCHS and a polyalanine expansion mutation are detected. 
     
     
         29 . The method of  claim 25 , wherein the polyalanine expansion mutation is detected in somatic cells. 
     
     
         30 . The method of  claim 25 , wherein the biological sample is selected from the group consisting of blood, white blood cells, epithelial cells, skin, hair, fibroblasts, a tissue from an organ, amniocytes, chorionic villi, embryonic cells, sperm and combinations thereof. 
     
     
         31 . A method of detecting a polyalanine repeat expansion mutation in at least one allele of a human PHOX2b gene of a human subject, the method comprising analyzing whether a sample from the subject has a polyalanine repeat expansion mutation in exon 3 in at least one allele of the human PHOX2b gene, wherein the polyalanine repeat expansion mutation encodes up to 33 alanine residues. 
     
     
         32 . The method of  claim 31 , wherein the polyalanine expansion mutation is detected by a polymerase chain reaction and gel electrophoresis. 
     
     
         33 . The method of  claim 31 , wherein at least 95% of the human subjects with CCHS and a polyalanine expansion mutation are detected.