Sodium/bicarbonate cotransporter which plays an important role in regulating intracellular pH (PubMed:10993873, PubMed:20566632). Has been shown to act as a sodium/bicarbonate cotransporter in exchange for intracellular chloride (PubMed:10993873, PubMed:20566632). Has also been shown to act as a sodium/biocarbonate cotransporter which is not responsible for net efflux of chloride, with the observed chloride efflux being due to chloride self-exchange (By similarity). Controls neuronal pH and may contribute to the secretion of cerebrospinal fluid (PubMed:18165320). Reduces the excitability of CA1 pyramidal neurons and modulates short-term synaptic plasticity (PubMed:26136660). Required in retinal cells to maintain normal pH which is necessary for normal vision (PubMed:23056253). In the kidney, likely to mediate bicarbonate reclamation in the apical membrane of the proximal tubules (By similarity). Detected in dendrites and axon terminals of retinal OFF bipolar cells and in axon terminals of ON bipolar cells (PubMed:23056253). In amacrine cells, located in the perikaryon (PubMed:23056253). Also detected in basal and apical dendrites of hippocampal pyramidal cells (PubMed:18165320). The use of 2 alternative promoters gives rise to isoforms which differ at the N-terminus. In addition, alternative splicing gives rise to further isoform diversity. In the brain, detected in cerebral cortex, subcortex, cerebellum, hippocampus and medulla (at protein level) (PubMed:20541593, PubMed:18061361, PubMed:21439947, PubMed:24905082). In the cerebrum, expressed at high levels throughout the cortex, at lower levels in striatum and not detectable in the corpus callosum (at protein level) (PubMed:20541593). In the cerebellum, detected at high levels in the molecular layer but at very low levels in the granular layer (at protein level) (PubMed:20541593). In the central nervous system, detected in neurons in the olfactory bulb, cortex and cerebellum (at protein level) (PubMed:18165320). Within the hippocampus, abundantly expressed in CA3 pyramidal cells (at protein level) (PubMed:18165320). Strongly expressed in the retina with high levels in bipolar and amacrine cells (at protein level) (PubMed:23056253). Expressed at high levels in brain and at low levels in the pituitary, testis, kidney and ileum (PubMed:10993873). Also expressed in pancreatic islets (PubMed:10993873). Expressed in the epithelial cells of the choroid plexus (PubMed:14592810, PubMed:15567717). During embryonic development, expressed in neurons of the central nervous system (PubMed:15567717). Also expressed in the peripheral nervous system and in non-neuronal tissues such as the dura and some epithelia including the acid-secreting epithelium of the stomach and the duodenal epithelium (PubMed:15567717). In the embryonic retina, expression is restricted to the neuronal cell layer and the retinal pigment epithelium (PubMed:15567717). In the embryonic central nervous system, detected at 12.5 dpc when expression is observed in all areas of the brain including the cerebellum (PubMed:15567717). In the embryonic cerebral cortex, detected at 14.5 dpc with levels increasing at 18.5 dpc (PubMed:15567717). Repressed in the brain by chronic continuous hypoxia (at protein level). The N-terminal cytoplasmic domain is likely to have a high level of intrinsic disorder. N-glycosylated. Homozygotes are born at the expected Mendelian ratio but most pups die around weaning (PubMed:18165320). When fed soft food from the second week of life onward, most pups catch up with the weight of their wild-type littermates and survive (PubMed:18165320). Adults display normal weight and lifespan, are fertile and do not display major behavioral abnormalities (PubMed:18165320). However, brain ventricle size is drastically reduced and mutants show diminished Na(+)-dependent recovery of pH following acid loading of choroid plexus epithelial cells (PubMed:18165320). Mutants also show reduced excitability of CA3 pyramidal neurson and have increased seizure threshold (PubMed:18165320). Increased excitability of CA1 pyramidal neurons and diminished paired pulse facilitation in the hippocampus (PubMed:26136660). No obvious morphological changes in the retina but mutants display decreased visual acuity and contrast sensitivity in behavioral experiments, smaller scotopic and photopic b-wave amplitudes and longer latencies in electroretinograms, and altered temporal response properties of ganglion cells (PubMed:23056253). Belongs to the anion exchanger (TC 2.A.31) family. Has been shown to act as a sodium/bicarbonate cotransporter in exchange for intracellular chloride (PubMed:10993873, PubMed:20566632). Has also been shown to act as a sodium/biocarbonate cotransporter which is not responsible for net efflux of chloride, with the observed chloride efflux being due to chloride self-exchange (By similarity). Extended N-terminus.