SummaryWe sequenced the SERPINC1 gene in 26 patients (11 males) with antithrombin (AT) deficiency (22 type I, 4 type II), belonging to 18 unrelated families from Southern Italy. Heterozygous mutations were identified in 15/18 (83.3%) families. Of them, eight were novel mutations, each being identified in one family. Seven clearly cause impaired protein synthesis (four frameshift, one non-stop, one splicing and one 21bp deletion). One, present in a single patient, is a missense mutation thought to be causative because: a) it is absent in 100 chromosomes from controls; b) it involves a highly conserved amino acid, whose change is predicted to impair AT activity; c) no other mutation is present in the propositus. Severe mutations (i.e. nonsense, frameshift, deletions) were invariably identified in type I patients. In type II patients, 3/4 were missense mutations; the fourth leads to a 19 nucleotides shift in the stop codon. In addition to the type of mutation, the co-existence of other predisposing factors in most patients helps explain the severity of the present type I cases (age at first event, recurrence during prophylaxis). In the five families in which there was more than one member affected, the same genotype and a concordant clinical expression of the disease were found. We conclude that the molecular bases of AT deficiency in Southern Italy are different as compared to other geographic areas, and that molecular analysis and the study of the effect of the mutation may help predict the clinical expression of the disease.

Approximately 90% of patients with osteogenesis imperfecta (OI) exhibit dominant COL1A1 or COL1A2 mutations; however, molecular analysis is difficult because these genes span 51 and 52 exons, respectively. We devised a PCR-denaturing high-performance liquid chromatography (DHPLC) procedure to analyze the COL1A1 or COL1A2 coding regions and validated it using 130 DNA samples from individuals without OI, 25 DNA samples from two cells to investigate the procedure's potential for preimplantation diagnosis, and DNA samples from 10 patients with OI. Three novel intronic variants in vitro were expressed using a minigene assay to assess their effects on splicing. The procedure is rapid, inexpensive, and reproducible. Analysis of samples from individuals without OI revealed six novel and some known polymorphisms useful for linkage diagnosis because of high heterozygosity. Analysis of two-cell samples confirmed the known genotype in 24 of 25 experiments; DNA failed to amplify in only one case. No incidence of allele dropout was recorded. DHPLC revealed six novel mutations, three of which were intronic, in all patients with OI, and these results were confirmed by means of COL1A1 and COL1A2 direct sequencing. Expression of intronic mutations demonstrated that variant 804 + 2_804 + 3delTG in intron 11 disrupts normal splicing, thereby leading to formation of two alternative products. Variants c.3046-4_3046-5dupCT (COL1A1) and c.891 + 77A>T (COL1A2) did not affect splicing. The described DHPLC protocol combined with the minigene assay may contribute to molecular diagnosis in OI. Moreover, this protocol will aid in counseling about prenatal and preimplantation diagnosis.

PD in well-equipped laboratories, and multidisciplinary counselling are an aid to planning reproductive and early therapeutic strategies in families with severe haemophilia.

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