Two novel alleles at HLA-B locus identified in two volunteer bone marrow donors by sequence-based typing.

Two novel human leucocyte antigen (HLA) class I alleles have been identified in two Italian individuals. HLA-B*27:07:02 is identical to HLA-B*27:07:01 except for a nucleotide substitution at position 846 (A->G) resulting in a silent mutation. HLA-B*35:206 differs from the most similar allele, HLA-B*35:08:01, because of a single base mutation at position 149 (G->C) causing an aminoacidic change at codon 26 from Gly to Ala.

Ethical implications of predictive DNA testing for hereditary breast cancer.

Predictive medicine offers the possibility of detecting many common diseases that have a genetic basis, such as cancer; however, a genetic alteration might only indicate susceptibility to, not certainty of, disease. Whereas means for identifying a greater susceptibility to disease have been developed, effective interventions have progressed much more slowly. Awareness of one's susceptibility to disease without an actual possibility of intervention can lead to an unacceptable use of such information, or have a dramatic psychological impact on the person involved. Are the risks connected with the knowledge of susceptibility to genetic disease proportional to the benefits that such knowledge may provide? Does the knowledge of one's genetic condition constitute a service to the individual and society, or is this predominantly harmful for the person involved? The problem is vast, and involves medical, psychological, social, political and ethical dilemmas. These dilemmas, common to all predictive medicine, are most evident in predictive DNA testing for hereditary breast cancer. In our analysis, we will first examine the ethical values involved in genetic testing, highlighting the special ethical issues raised by predictive DNA testing for hereditary breast cancer. Next we will deal with genetic counseling, which, in our opinion, is the 'ethos' for ethically justifying predictive DNA testing.

An immunogenetic map of Lombardy (Northern Italy).

For this study we consulted the Bone Marrow Donors' Registry of Lombardy (Italy) and analyzed 43937 HLA-A,B phenotypes and 13922 HLA-A,B,DR phenotypes. We estimated the HLA-A,B and HLA-A,B,DR haplotype frequencies via the maximum-likelihood method. We analyzed the genetic structure of the 11 provinces of Lombardy by means of Principal Component Analysis and Correspondence Analysis, and estimated the variety of the different haplotypes at provincial level and the percentage of unique phenotypes at village level. We found 11189 different HLA-A,B phenotypes, 661 different HLA-A,B haplotypes and more than 4000 different HLA-A,B,DR haplotypes. We identified 20 villages, in Western Lombardy, very rich in unique/rare phenotypes. Here we report a formula which allows the identification of a putative donor matched for two haplotypes with a recipient. This result may be of great importance for the genetic study of the population of Lombardy and, even more, for bone marrow transplantation programs.

Premature termination mutations in exon 3 of the SMN1 gene are associated with exon skipping and a relatively mild SMA phenotype.

Autosomal recessive spinal muscular atrophy (SMA) is a common motor neuron disease caused by absence or mutation in the survival motor neuron (SMN1) gene. SNM1 and a nearly identical copy, SMN2, encode identical proteins, but SMN2 only produces a little full length protein due to alternative splicing. The level of functional SMN protein and the number of SMN2 genes correlate with the clinical phenotype ranging from severe to very mild. Here, we report on premature termination mutations in SMN1 exon 3 (425del5 and W102X) which induce skipping of the mutated exon. The novel nonsense mutation W102X was detected in two patients with a relatively mild phenotype who had only two copies of the SMN2 gene, a number that has previously been found associated with the severe form of SMA. We show that the shortened transcripts are translated into predicted in frame protein isoforms. Aminoglycoside treatment suppressed the nonsense mutation in cultured cells and abolished exon skipping. Fibroblasts from both patients show a high number of nuclear structures containing SMN protein (gems). These findings suggest that the protein isoform lacking the exon 3 encoded region contributes to the formation of the nuclear protein complex which may account for the milder clinical phenotype.

Detection of the survival motor neuron (SMN) genes by FISH: further evidence for a role for SMN2 in the modulation of disease severity in SMA patients.

Spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disorder which presents with various clinical phenotypes ranging from severe to very mild. All forms are caused by the homozygous absence of the survival motor neuron ( SMN1 ) gene. SMN1 and a nearly identical copy ( SMN2 ) are located in a duplicated region at 5q13 and encode identical proteins. The genetic basis for the clinical variability of SMA remains unclear, but it has been suggested that the copy number of SMN2 could influence the disease severity. We have assessed the number of SMN2 genes in patients with different clinical phenotypes by fluorescence in situ hybridization (FISH) using as SMN probe a mixture of small specific DNA fragments. Gene copy number was established by FISH on interphase nuclei, but the presence of two SMN2 genes on the same chromosome could also be revealed by FISH on metaphase spreads. All patients had at least two SMN2 genes. We found two or three copies of SMN2 in severely affected type I patients, three copies in intermediately affected type II patients, generally four copies in mildly affected type III patients and four or eight copies in patients with very mild adult-onset SMA. No alterations of the genes were detected by Southern blot and sequence analysis, suggesting that all gene copies of SMN2 were intact. These data provide additional evidence that the SMN2 genes modulate the disease severity and suggest that knowledge of the gene copy number could be of some prognostic value.