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Introduction: Cerebral small vessel diseases (CSVDs) are an important cause of stroke, cognitive impairment, and mood disorders among the elderly. Usually CSVD is sporadic, but early-onset monogenic forms of CSVD have been reported. CADASIL is one of the most common hereditary CSVD caused by autosomal dominant NOTCH3 gene mutations, while CARASIL is a rare autosomal recessive CSVD caused by HTRA1 gene mutations. More than 200 mutations are known in NOTCH3 gene and only 12 HTRA1 mutated CARASIL families have been reported so far. Recently, heterozygous HTRA1 mutations have been described associated with an autosomal dominant form of CSVD with reduced penetrance, showing clinical features differing from those of CARASIL. Patients and methods: We report a family with three affected individuals, referred for stroke and cognitive impairment segregating as an autosomal dominant disorder. Mutations in NOTCH3 and HTRA1 genes have been screened by Sanger sequencing. In silico prediction tools PolyPhen and SIFT have been used to predict the pathogenicity of the variants found. Skin biopsy of one patient was examined with transmission electron microscope. Results: A heterozygous HTRA1 missense mutation segregating with the disease and predicted to be deleterious has been found. The mutation affects a highly conserved aminoacid, which, if mutated, strongly reduce the HTRA1 proteolytic activity. The biopsy showed deposits of osmophilic material in the arterial wall, very similar to those characterizing CADASIL. Conclusions: We confirm the dominant inheritance of some HTRA1 mutations, overlapping clinical, MRI and ultramicroscopic features of CADASIL, in absence of the typical CARASIL extra-neurological symptoms.

The CACNA1A gene codes for the alpha(1A) pore-forming subunit of Ca(2+) voltage-gated Cav2.1 channels. CACNA1A mutations are responsible for Familial Hemiplegic Migraine (FHM) type 1, Episodic Ataxia (EA) type 2 and Spinocerebellar Ataxia type 6. The structure of the human gene includes, at present, 49 exons; however almost nothing is known about the 5' regulatory region, and there is now evidence suggesting the presence of additional exons at the 3' of the gene. The 892 bp fragment upstream of exon 1 and its deletion mutants were characterised for their transcriptional activity by using luciferase as a reporter gene. The 3' region was analysed by Rapid Amplification of the cDNA 3' End. Both regions were screened for mutations in a series of FHM and EA patients by SSCP and sequencing. At the 5' end of the gene a minimal promoter region was identified within the first 497 bp from ATG. By screening a larger fragment for mutations, the 5 bp deletion (g.-757_-753delCTTTC) was identified in a FHM patient. The deletion significantly increased the transcriptional activity, most likely due to the removal of half a turn of the DNA helix, changing the orientation of downstream binding sites for transcriptional factors. At the 3' end of the gene a new exon 48, followed by a strong poly-A signal, was identified as well as a new splice variant. The 5 bp insertion (g.38429_38430insCTTTT) in this exon was found in an EA patient. The two new regions can open the way for the study of human CACNA1A gene expression regulation and can be sites of mutations associated with FHM or EA phenotypes.