title: Tissue specific expression of alternative splice forms of human cyclic nucleotide gated channel subunit CNGA3.
abstract: OBJECTIVE
  The cyclic nucleotide gated cation channel subunit, CNGA3, (also known as the cone alpha CNG subunit), plays a vital role in signal transduction of human cone cells. Owing to its well established role in vision, the human CNGA3 isoform studied thus far was cloned from retinal tissue. However, non-human homologs of CNGA3 have been cloned from a variety of other tissues including kidney, heart, pineal gland, adrenal gland and testes. Among these, alternative splice forms of CNGA3 have been identified. The objective of this study was to explore alternative splice forms of human CNGA3 and determine their distribution among various human tissues.
  
  
  METHODS
  RT-PCR was used to amplify full length open reading frames of CNGA3 from human testes RNA and to detect and distinguish among splice forms in 23 tissues. DNA sequencing was used to characterize full length splice forms and to confirm the identity of RT-PCR products from a number of tissues.
  
  
  RESULTS
  Two new full length alternatively spliced forms of hCNGA3 (referred to as Variant 2 and 3) were isolated. These splice variants are different from the cone hCNGA3 (Variant 1) in that they lack exon 5. In addition, they differ from each other in that Variant 3 contains an extra exon that originates from the intron preceding exon 4. We demonstrate that CNGA3 transcripts are detectable in all 23 human tissues examined. In all tissues, except retina, Variant 2 specific PCR products had the brightest band intensity. In retina, the band from Variant 1 (containing exon 5) was most intense. In fact, among all tissues examined, Variant 1 can only be detected strongly in the retina.
  
  
  CONCLUSIONS
  The extensive distribution of CNGA3 and the tissue specific expression of alternative splice forms indicate widespread and diverse roles for CNGA3. The unique expression of Variant 1 in the retina implies a significance to the amino acids encoded by exon 5 that may be necessary for the function of CNGA3 in human cone cells.
authors.affiliation: Neuroscience Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064-6117, USA. steven.cassar@abbott.com
authors.forename: Steven C
authors.initials: SC
authors.lastname: Cassar
authors.forename: Jun
authors.initials: J
authors.lastname: Chen
authors.forename: Di
authors.initials: D
authors.lastname: Zhang
authors.forename: Murali
authors.initials: M
authors.lastname: Gopalakrishnan
mesh_terms: D017398:Alternative Splicing / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D054815:Cyclic Nucleotide-Gated Cation Channels; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D006801:Humans; D007473:Ion Channels / Q000235:genetics* / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013737:Testis / Q000378:metabolism; D014018:Tissue Distribution
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; D005136:Eye Proteins; D007473:Ion Channels; D012333:RNA, Messenger