For example, mice homozygous for the Col4a1 G498V mutation, detected in HANAC patients, are viable (21) in contrast to other glycine mutations in mice (4,18,19), while other non-glycine mutations do not appear to cause ER stress (24) and presumably act though matrix defects. The gene discussed is COL4A1; the disease is autosomal dominant familial hematuria-retinal arteriolar tortuosity-contractures syndrome.