New insight into the effects of heparinoids on complement inhibition by C1-inhibitor.

Complement activation is of major importance in numerous pathological conditions. Therefore, targeted complement inhibition is a promising therapeutic strategy. C1-esterase inhibitor (C1-INH) controls activation of the classical pathway (CP) and the lectin pathway (LP). However, conflicting data exist on inhibition of the alternative pathway (AP) by C1-INH. The inhibitory capacity of C1-INH for the CP is potentiated by heparin and other glycosaminoglycans, but no data exist for the LP and AP. The current study investigates the effects of C1-INH in the presence or absence of different clinically used heparinoids on the CP, LP and AP. Furthermore, the combined effects of heparinoids and C1-INH on coagulation were investigated. C1-INH, heparinoids or combinations were analysed in a dose-dependent fashion in the presence of pooled serum. Functional complement activities were measured simultaneously using the Wielisa(®) -kit. The activated partial thrombin time was determined using an automated coagulation analyser. The results showed that all three complement pathways were inhibited significantly by C1-INH or heparinoids. Next to their individual effects on complement activation, heparinoids also enhanced the inhibitory capacity of C1-INH significantly on the CP and LP. For the AP, significant potentiation of C1-INH by heparinoids was found; however, this was restricted to certain concentration ranges. At low concentrations the effect on blood coagulation by combining heparinoids with C1-INH was minimal. In conclusion, our study shows significant potentiating effects of heparinoids on the inhibition of all complement pathways by C1-INH. Therefore, their combined use is a promising and a potentially cost-effective treatment option for complement-mediated diseases.

Possibilities and barriers in the implementation of a preconceptional screening programme for cystic fibrosis carriers: a focus group study.

OBJECTIVE: This qualitative study aimed to explore possibilities and barriers in the implementation of a nationwide preconceptional cystic fibrosis (CF) carrier screening programme. METHODS: Sessions were held with two focus groups of CF patients and CF relatives, one focus group of people from the target population (couples planning a pregnancy), and two focus groups of potential providers (general practitioners (GPs) and municipal health service workers). RESULTS: Important barriers in the implementation of a preconceptional CF carrier screening programme included the problem of reaching the target population, the heavy workload of GPs, the limited public knowledge about CF in general, and the absence of a preconceptional consultation setting. In general, there was a positive attitude among the participants towards CF carrier screening. CONCLUSION: This study revealed some important barriers in the implementation of CF carrier screening programmes. More research is needed to specify and quantify the importance of the various barriers. Eventually, different intervention strategies should be included in an implementation plan to overcome the most important barriers in the organization and execution of screening.

[Sex-linked mental retardation]. / Geslachtsgebonden mentale retardatie.

It has long been known that among patients with mental retardation males outnumber females. This is the result of mutations in X-chromosomal genes: X-linked mental retardation. Its prevalence has been estimated as 1.8/1000 males with a carrier frequency of 2.4/1000 females. X-linked mental retardation is divided into syndromic and non-specific types. At present there are about 135 syndromic forms known of 26 of which the responsible genes and mutations have been found. 8 genes are known in which mutations have been found in non-specific X-linked mental retardation. It is estimated that about 100 genes are involved in the latter. These genes are in particular involved in the function of the central nervous system. The development of a complete genetic map of the X-chromosome and the introduction of microarray techniques will in the short term enormously enhance the elucidation of X-linked mental retardation.

A novel ribosomal S6-kinase (RSK4; RPS6KA6) is commonly deleted in patients with complex X-linked mental retardation.

Large deletions in Xq21 often are associated with contiguous gene syndromes consisting of X-linked deafness type 3 (DFN3), mental retardation (MRX), and choroideremia (CHM). The identification of deletions associated with classic CHM or DFN3 facilitated the positional cloning of the underlying genes, REP-1 and POU3F4, respectively, and enabled the positioning of the MRX gene in between these genes. Here, we report the cloning and characterization of a novel gene, ribosomal S6-kinase 4 (RSK4; HGMW-approved symbol RPS6KA6), which maps in the MRX critical region. RSK4 is completely deleted in eight patients with the contiguous gene syndrome including MRX, partially deleted in a patient with DFN3 and present in patients with an Xq21 deletion and normal intellectual abilities. RSK4 is most abundantly expressed in brain and kidney. The predicted protein of 746 amino acids shows a high level of homology to three previously isolated members of the human RSK family. RSK2 is involved in Coffin-Lowry syndrome and nonspecific MRX. The localization of RSK4 in the interval that is commonly deleted in mentally retarded males together with the high degree of amino acid identity with RSK2 suggests that RSK4 plays a role in normal neuronal development. Further mutation analyses in males with X-linked mental retardation must prove that RSK4 is indeed a novel MRX gene.

Genetic fine mapping of the gene for recessive Stargardt disease.

Stargardt disease (STGD) is one of the most frequent causes of macular degeneration in childhood. Linkage analysis in families with recessive STGD has recently shown genetic homogeneity and a location of the underlying gene at 1p22-p21 in a 4-cM interval. Haplotype analysis in seven Dutch STGD families with 11 highly polymorphic markers spanning the critical region has enabled us to refine the location of the underlying gene to a 2-cM region flanked by the loci D1S406 and D1S236. We have identified one 45-year-old nonpenetrant individual who carries two disease alleles. In another family, an affected individual inherited the paternal but not the maternal disease chromosome, suggesting genetic heterogeneity or a different mechanism leading to the disease in this family.