For example, the mutation of TGFβ1 repressor HTRA1 would induce cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) [140], frameshift deletions in the three-prime repair exonuclease 1 (TREX1) gene mediating the onset of autosomal dominant retinal vasculopathy characterized by cerebral leukodystrophy [141], and mutations in the type-IV collagen alpha 1 (COL4A1) gene, encoding the COL4A1 chain, are also significantly associated with leukoencephalopathy and intracranial hemorrhage [142]. Here, HTRA1 is linked to CARASIL.