Characterisation of the human voltage-gated potassium channel gene, KCNA7, a candidate gene for inherited cardiac disorders, and its exclusion as cause of progressive familial heart block I (PFHBI)

Abstract

Mutations in genes encoding cardiac ion channels and their subunits are responsible for several genetic cardiac disorders. We characterised the human gene KCNA7, encoding the voltage-gated potassium channel Kv1.7 and compared its coding sequence with that of the mouse orthologue, kcna7. Both genes are encoded by two exons separated by a conserved intron, unlike all the other Kv1-family genes that contain intronless coding regions. KCNA7 and kcna7 encode proteins of 456 amino acid residues that share 495% sequence identity, and the mouse channel has biophysical and pharmacological properties closely resembling the ultrarapidly activating delayed rectifier (I Kur ) in cardiac tissue. Using reverse transcriptase-PCR, KCNA7 mRNA was detected in adult human heart. We determined that KCNA7 resides on chromosome 19q13.3 in a region that also contains the progressive familial heart block I (PFHBI) locus. Direct sequencing of KCNA7's coding sequence in PFHB1-affected individuals revealed no pathogenic sequence changes, but two single nucleotide polymorphisms detected in exon 2 result in amino acid substitutions. These results provide evidence for the exclusion of this candidate as the PFHB1-causative gene, although mutations in regulatory and non-coding regions cannot be excluded. As ion channel-encoding genes have been implicated in a growing number of genetic conditions, the data presented may facilitate further analysis of the role of KCNA7 and its product in the heart.

Impaired endocytosis of the ion channel TRPM4 is associated with human progressive familial heart block type I

“…Of these 25 genes, 5 are expressed in cardiac tissue: U1 small nuclear ribonucleoprotein (SNRP70); histidine-rich calcium-binding protein (HRC); transient receptor potential cation channel, subfamily M, member 4 (TRPM4); transcriptional enhancer 4 (TEAD2); and potassium voltage-gated channel, Shaker-related subfamily, member7 (KCNA7) (11,(14)(15)(16)(17)(18). Previously, KCNA7 was excluded as a possible candidate gene (16). Here, we focused on TRPM4 (11), which was prominently expressed in human Purkinje fibers compared with septum, atrium, and right and left ventricles ( Figure 2A).…”

Design of PAP-1, a Selective Small Molecule Kv1.3 Blocker, for the Suppression of Effector Memory T Cells in Autoimmune Diseases

“…EC 50 values and Hill coefficients were determined by fitting the Hill equation to the reduction of area under the current curve measured at 40 mV. Kv1.1, Kv1.5, Kv1.4, Kv1.6, Kv1.7, Kv2.1, Kv3.1, Kv3.2, and Kv4.2 currents were recorded with 200-ms depolarizing pulses to 40 mV applied every 10 s (Grissmer et al, 1994;Wulff et al, 2000;Bardien-Kruger et al, 2002). For Kv1.2, we applied 200-ms pulses to 40 mV every 5 s to allow for the channel's use-dependent activation (Grissmer et al, 1994).…”

Kv1.3-Blocking 5-Phenylalkoxypsoralens: A New Class of Immunomodulators

“…EC 50 values and Hill coefficients were determined by fitting the Hill equation to the reduction of peak current measured at 40 mV. Kv1.1, Kv1.5, Kv1.7, Kv1.4, and Kv3.1 currents were recorded with 200-ms depolarizing pulses to 40 mV applied every 10 s (Grissmer et al, 1994;Wulff et al, 2000;Bardien-Kruger et al, 2002). For Kv1.2, we applied 200-ms pulses to 40 mV every 5 s to allow for the use-dependent activation of the channel (Grissmer et al, 1994).…”

“…LTK cells expressing hKv1.4 were obtained from M. Tamkun (University of Colorado, Boulder, Boulder, CO), human embryonic kidney-293 cells expressing hSlo␣ were obtained from A. Tinker (Centre for Clinical Pharmacology, University College London, London, UK), human embryonic kidney-293 cells expressing HERG (Kv11.1) were obtained from C. T. January (Department of Medicine, The University of Wisconsin-Madison, Madison, WI), and N1E-115 neuroblastoma cells were obtained from B. Hamprecht (Physiologisch-Chemisches Institut, Universitä t Tü bingen, Tü bingen, Germany). hIKCa1 (hK Ca 3.1), hSKCa3 (hK Ca 2.3), and mKv1.7 were cloned as described previously Bardien-Kruger et al, 2002) and transiently transfected into COS-7 cells using FuGene 6 (Roche Diagnostics, Indianapolis, IN) according to the manufacturer's protocol. …”