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Mutations in the small heat-shock protein 27 kDa protein 1 (HSPB1) and 22 kDa protein 8 (HSPB8) genes were associated with distal hereditary motor neuropathy (dHMN) and with the axonal form of Charcot-Marie-Tooth disease type 2 (CMT2). Here we report the clinical and molecular evaluation of an Italian dHMN and CMT2 cohort to establish HSPB1 and HSPB8 mutation occurrence and associated clinical features. One hundred and sixty-seven patients with dHMN or CMT2 were studied. HSPB1 and HSPB8 exons 1 and 3 molecular analysis was carried out through DHPLC and direct sequencing of each variant chromatogram. HSPB8 exon 2 was analyzed by direct sequencing. Four mutations in five unrelated dHMN patients and four mutations in four unrelated CMT2 cases were found in HSPB1. The p.Arg136Leu mutation was found in two patients with different phenotypes. Electroneurographical follow-up study in a dHMN patient revealed that sensory impairment occurred with disease progression. The HSPB1 mutation frequency was 8% in dHMN and 4% in CMT2 patients. The significant HSPB1 mutation frequency in both phenotypes indicates its relevance in the pathogenesis of these neuropathies. Recent literature data suggest a continuum between dHMN and CMT2. We confirm this finding in our cohort, proposing a definite relationship between these disorders.

Germline mutations within the coding region of CDKN2A have been observed in affected members of melanoma-prone families. G101W is the most common CDKN2A missense mutation identified to date. It has been reported in several families from around the world, with a particularly high occurrence in France and Italy. Given the frequency of this mutation, we were interested in determining whether the mutation resulted from a single origin or represented a mutational hotspot in the CDKN2A gene. In addition, given the geographical distribution of the mutation, we examined the date of origination of the mutation and its migratory spread. We examined 10 families from Italy, 4 families from the United States, and 6 families from France with the G101W mutation. The following eight markers were employed for the haplotype analysis: IFNA, D9S736, D9S1749, D9S942, D9S1748, D9S1604, D9S171, and D9S126. Our findings showed no significant evidence for mutational heterogeneity, suggesting that all studied families derived from a single ancestral haplotype on which the mutation arose. Using maximum-likelihood methods, we estimated the mutation to have arisen 97 generations ago (1-LOD-unit support interval 70-133 generations) providing some explanation for the wide geographical spread of this common mutation, particularly in southwestern Europe. The presence of a founder mutation in a defined geographic area can facilitate carrier detection and genetic counseling and can provide an opportunity to study disease penetrance and the effect of environmental factors on the background of a common genetic susceptibility.

CDKN2A germline mutation frequency estimates are commonly based on families with several melanoma cases. When we started counseling in a research setting on gene susceptibility analysis in northern and central Italy, however, we mostly found small families with few cases. Here we briefly characterize those kindred, estimate CDKN2A/CDK4 mutation test yields, and provide indications on the possibility of implementing formal DNA testing for melanoma-prone families in Italy. In September 1995 we started genetic counseling in a research setting at our Medical Genetics Center. Screening for CDKN2A/CDK4 mutations was performed on families with two melanoma patients, one of whom was younger than 50 years at onset, the other complying with one of the following: 1) being a first-degree relative, 2) having an additional relative with pancreatic cancer, or 3) having multiple primary melanomas. Sixty-two of 67 (80%) melanoma cases met our criteria. Four previously described CDKN2A mutations (G101W, R24P, V126D, and N71S) were found in 21 of the 62 families (34%) with a high prevalence of G101W (18/21). The percentage of families with two melanoma cases/family harboring a mutation was low (7%, 2/27), but rose to 45% (9/20) if one of the melanoma patients carried multiple melanomas or if pancreatic cancer was present in that family. In the 15 families with three melanoma cases the presence of a mutation was higher (67%, 10/15) and reached 100% in the 4 families with four or more melanoma cases. Our results suggest that CDKN2A/CDK4 counseling-based mutational analysis may be reasonably efficient also for families with two melanoma cases, if one patient carries multiple melanomas or if pancreatic cancer is present in the family.

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Two genes were identified for autosomal recessive forms of early onset Parkinson's disease: parkin and DJ-1. We describe 2 siblings with EOPD due to parkin mutations and peripheral neuropathy, which presented as neuropathy with liability to pressure palsies (HNPP) in the index case. RT-PCR experiments revealed that the parkin gene is expressed in sural nerves from both controls and patient with parkin-related disease. Our findings support the view that parkin may play a role in the peripheral nervous system.

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Mutations in small heat-shock protein 27 and small heat-shock protein 22 genes were found in association with Charcot-Marie-Tooth disease type 2 and distal hereditary motor neuropathy. We searched for mutations in small heat-shock protein 27 gene in an Italian family with peripheral neuropathy and intrafamilial phenotypic variability. A novel heterozygous frame-shift mutation c.476_477delCT was found while point mutations in most genes associated with hereditary neuropathies were ruled out. In the proband, who showed a severe early onset peripheral neuropathy, an independent pathogenetic effect on the peripheral nervous system secondary to the tetanus toxoid injection may be supposed. This is the first truncating nonsense mutation in the small heat-shock protein 27 gene identified so far and the clinical, neurophysiologic, and neuropathological findings are discussed.