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FLASH GENE

Symbol

GJA8

contributors: mct/shn - updated : 03-10-2011

HGNC name	gap junction protein, alpha 8, 50kDa
HGNC id	4281

FLASH GENE DNA RNA EXPRESSION PROTEIN DISORDER ANIMAL & CELL MODELS

Corresponding disease	CATR cataract triangular CZP1 cataract, zonular pulverulent 1
Location	1q21.2      Physical location : 147.374.945 - 147.381.393
Synonym name	lens intrinsic membrane protein MP70
	lens fiber protein MP70
	gap junction protein, alpha 8, 50kDa (connexin 50)
	gap junction membrane channel protein alpha-8
	connexin 50
	connexin-50
	cell surface glycoprotein
Synonym symbol(s)	CX50, MIP4, MP70, CAE, CAE1, CZP1

DNA

TYPE	functioning gene
STRUCTURE	6.45 kb     2 Exon(s)

Genomic sequence alignment details
10 Kb 5' upstream gene genomic sequence study

MAPPING

cloned

Y

linked

N

status

confirmed

Map	cen - D1S2344 - D1S442 - GJA8 - D1S2612 - D1S3466 - qter

RNA

TRANSCRIPTS	type	messenger

identification nb exons type bp product Protein kDa AA specific expression Year Pubmed NM_005267 2 - 1377 NP_005258 48.1 433 - 1995 8549164

EXPRESSION

Type	restricted

expressed in	(based on citations)
organ(s)	System Organ level 1 Organ level 2 Organ level 3 Organ level 4 Level Pubmed Species Stage Rna symbol Visual eye lens     specific

tissue

System Tissue Tissue level 1 Tissue level 2 Level Pubmed Species Stage Rna symbol Epithelial barrier lining retinal pigment epithelium (RPE)

cell lineage

cell lines

fluid/secretion

at STAGE

physiological period

fetal

Text

eye

PROTEIN

PHYSICAL PROPERTIES

STRUCTURE

motifs/domains	four putative membrane spanning alpha helices, separating the N terminal intracellular domain
	two extracellular loops
	a C terminal intracellular domain, involved in pHi sensitivity, but has little influence over single-channel conductance, voltage dependence, or gating kinetics

HOMOLOGY

interspecies	ortholog to Gja8, Mus musculus
	ortholog to Gja8, Rattus norvegicus
	ortholog to GJA8, Pan troglodytes

Homologene

FAMILY	connexin family
	alpha-type (group II) subfamily

CATEGORY

structural protein , transport channel

SUBCELLULAR LOCALIZATION

plasma membrane

basic FUNCTION	playing a critical role for maintenance of lens transparency (
	required for normal eye growth (
	having water channel properties
	gap junction channels formed by GJA8 are critical for the maintenance of eye lens transparency, which is sensitive to pH and external Ca2+ concentration
	essential for normal lens development

CELLULAR PROCESS	cell life, proliferation/growth

PHYSIOLOGICAL PROCESS

cell to cell transport

PATHWAY

metabolism

signaling

sensory transduction/vision

a component	monomer constituent of the connexon (six subunits including GJA3, GJA8, GJB1, GJB2), docking with its counterpart in the neighboring cell to form the gap junction channel
	major intrinsic protein constituent of lens fiber

INTERACTION

DNA

RNA

small molecule

protein	interacting with calmodulin (calmodulin and Ca2+ can cooperate in the gating control of GJA8 hemichannels)
	directly interacts with MIP in lens
	binding of Ca2+/CALM1 to the intracellular loop of GJA8 is critical for mediating the Ca2+-dependent inhibition of GJA8 gap junctions in the lens of the eye
	GJA8 requires an intact PDZ-binding motif and TJP1 for the formation of functional intercellular channels

cell & other

REGULATION

ASSOCIATED DISORDERS

corresponding disease(s)

CZP1 , CATR

Susceptibility

to schizophrenia

Variant & Polymorphism other	polymorphisms increasing the risk of schizophrenia

Candidate gene
Marker
Therapy target	targeted replacement of Cx50 with Cx46 in mice by genetic knock-in corrects defects in cellular differentiation and prevents cataracts, but normal growth is not restored (

ANIMAL & CELL MODELS

	Cx50-null mice exhibited microphthalmia and nuclear cataracts (
	deletion of Cx50 in mice results in reduced ocular growth and cataracts (