The necessity for KCC3-mediated cell volume regulation in the human nervous system has been demonstrated by the autosomal recessive human disease Andermann syndrome, caused by loss-of-function mutations in KCC3, which results in axonal swelling, periaxonal fluid accumulation, and neurodegeneration due to defective RVD (Boettger et al., 2003; Byun and Delpire, 2007). The gene discussed is SLC12A6; the disease is Corpus callosum agenesis - neuronopathy.