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Masotti A, Uva P, Davis-Keppen L, Basel-Vanagaite L, Cohen L, Pisaneschi E, Celluzzi A, Bencivenga P, Fang M, Tian M, Xu X, Cappa M, Dallapiccola B. Keppen-Lubinsky syndrome is caused by mutations in the inwardly rectifying K+ channel encoded by KCNJ6. Am J Hum Genet 2015; 96:295-300. [PMID: 25620207 DOI: 10.1016/j.ajhg.2014.12.011] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Accepted: 12/10/2014] [Indexed: 12/30/2022] Open
Abstract
Keppen-Lubinsky syndrome (KPLBS) is a rare disease mainly characterized by severe developmental delay and intellectual disability, microcephaly, large prominent eyes, a narrow nasal bridge, a tented upper lip, a high palate, an open mouth, tightly adherent skin, an aged appearance, and severe generalized lipodystrophy. We sequenced the exomes of three unrelated individuals affected by KPLBS and found de novo heterozygous mutations in KCNJ6 (GIRK2), which encodes an inwardly rectifying potassium channel and maps to the Down syndrome critical region between DIRK1A and DSCR4. In particular, two individuals shared an in-frame heterozygous deletion of three nucleotides (c.455_457del) leading to the loss of one amino acid (p.Thr152del). The third individual was heterozygous for a missense mutation (c.460G>A) which introduces an amino acid change from glycine to serine (p.Gly154Ser). In agreement with animal models, the present data suggest that these mutations severely impair the correct functioning of this potassium channel. Overall, these results establish KPLBS as a channelopathy and suggest that KCNJ6 (GIRK2) could also be a candidate gene for other lipodystrophies. We hope that these results will prompt investigations in this unexplored class of inwardly rectifying K(+) channels.
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Affiliation(s)
- Andrea Masotti
- Bambino Gesù Children's Hospital, Istituto di Ricovero e Cura a Carattere Scientifico, 00165 Rome, Italy.
| | - Paolo Uva
- CRS4 Bioinformatics Laboratory, Parco Scientifico e Tecnologico POLARIS, 09010 Pula, Cagliari, Italy
| | - Laura Davis-Keppen
- Sanford School of Medicine, University of South Dakota, Sioux Falls, SD 57105, USA
| | - Lina Basel-Vanagaite
- Pediatric Genetics Unit, Schneider Children's Medical Center of Israel, Petah Tikva 49202, Israel; Raphael Recanati Genetic Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva 49100, Israel; Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv 69978, Israel; Felsenstein Medical Research Center, Rabin Medical Center, Petah Tikva 49100, Israel
| | - Lior Cohen
- Raphael Recanati Genetic Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva 49100, Israel
| | - Elisa Pisaneschi
- Bambino Gesù Children's Hospital, Istituto di Ricovero e Cura a Carattere Scientifico, 00165 Rome, Italy
| | - Antonella Celluzzi
- Bambino Gesù Children's Hospital, Istituto di Ricovero e Cura a Carattere Scientifico, 00165 Rome, Italy
| | - Paola Bencivenga
- Bambino Gesù Children's Hospital, Istituto di Ricovero e Cura a Carattere Scientifico, 00165 Rome, Italy
| | | | | | - Xun Xu
- BGI Shenzhen, Shenzhen 518083, China.
| | - Marco Cappa
- Bambino Gesù Children's Hospital, Istituto di Ricovero e Cura a Carattere Scientifico, 00165 Rome, Italy
| | - Bruno Dallapiccola
- Bambino Gesù Children's Hospital, Istituto di Ricovero e Cura a Carattere Scientifico, 00165 Rome, Italy
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Guatteo E, Bengtson CP, Bernardi G, Mercuri NB. Voltage-Gated Calcium Channels Mediate Intracellular Calcium Increase inWeaverDopaminergic Neurons During Stimulation of D2and GABABReceptors. J Neurophysiol 2004; 92:3368-74. [PMID: 15240766 DOI: 10.1152/jn.00602.2004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The weaver ( wv) mutation affects the pore-forming region of the inwardly rectifying potassium channel (GIRK) leading to degeneration of cerebellar granule and midbrain dopaminergic neurons. The mutated channel ( wvGIRK) loses its potassium selectivity, allowing sodium (Na+) and possibly calcium ions (Ca2+) to enter the cell. Here we performed whole cell patch-clamp recordings combined with microfluorometry to investigate possible differences in calcium ([Ca2+]i) dynamics in native dopaminergic neurons (expressing the wvGIRK2 subunits) in the midbrain slice preparation from homozygous weaver ( wv/wv) and control (+/+) mice. Under resting conditions, [Ca2+]iwas similar in wv/wv compared with +/+ neurons. Activation of wvGIRK2 channels by D2and GABABreceptors increased [Ca2+]iin wv/wv neurons, whereas activation of wild-type channels decreased [Ca2+]iin +/+ neurons. The calcium rise in wv/wv neurons was abolished by antagonists of the voltage-gated calcium channels (VGCC); voltage clamp of the neuron at −60 mV; and hyperpolarization of the neuron to −80 mV or more, in current clamp, and was unaffected by TTX. Therefore we propose that wvGIRK2 channels in native dopamine neurons are not permeable to Ca2+, and when activated by D2and GABABreceptors they mediate membrane depolarization and an indirect Ca2+influx through VGCC rather than via wvGIRK2 channels. Such calcium influx may be the trigger for calcium-mediated excitotoxicity, responsible for selective neuronal death in weaver mice.
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Affiliation(s)
- Ezia Guatteo
- Laboratory of Experimental Neurology, Fondazione Santa Lucia Istituto di Ricovero e Cura a Carattere Scientifico, 00179 Rome, Italy
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Mark MD, Herlitze S. G-protein mediated gating of inward-rectifier K+ channels. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:5830-6. [PMID: 10998041 DOI: 10.1046/j.1432-1327.2000.01670.x] [Citation(s) in RCA: 179] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
G-protein regulated inward-rectifier potassium channels (GIRK) are part of a superfamily of inward-rectifier K+ channels which includes seven family members. To date four GIRK subunits, designated GIRK1-4 (also designated Kir3.1-4), have been identified in mammals, and GIRK5 has been found in Xenopus oocytes. GIRK channels exist in vivo both as homotetramers and heterotetramers. In contrast to the other mammalian GIRK family members, GIRK1 can not form functional channels by itself and has to assemble with GIRK2, 3 or 4. As the name implies, GIRK channels are modulated by G-proteins; they are also modulated by phosphatidylinositol 4,5-bisphosphate, intracellular sodium, ethanol and mechanical stretch. Recently a family of GTPase activating proteins known as regulators of G-protein signaling were shown to be the missing link for the fast deactivation kinetics of GIRK channels in native cells, which contrast with the slow kinetics observed in heterologously expressed channels. GIRK1, 2 and 3 are highly abundant in brain, while GIRK4 has limited distribution. Here, GIRK1/2 seems to be the predominant heterotetramer. In general, neuronal GIRK channels are involved in the regulation of the excitability of neurons and may contribute to the resting potential. Interestingly, only the GIRK1 and 4 subunits are distributed in the atrial and sinoatrial node cells of the heart and are involved in the regulation of cardiac rate. Our main objective of this review is to assess the current understanding of the G-protein modulation of GIRK channels and their physiological importance in mammals.
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Affiliation(s)
- M D Mark
- Department of Physiology II, University of Tübingen, Germany
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