Insights into the physiological function of the β‐amyloid precursor protein: beyond Alzheimer's disease

The β‐amyloid precursor protein (APP) has been extensively studied for its role as the precursor of the β‐amyloid protein (Aβ) of Alzheimer's disease. However, the normal function of APP remains largely unknown. This article reviews studies on the structure, expression and post‐translational processing of APP, as well as studies on the effects of APP in vitro and in vivo. We conclude that the published data provide strong evidence that APP has a trophic function. APP is likely to be involved in neural stem cell development, neuronal survival, neurite outgrowth and neurorepair. However, the mechanisms by which APP exerts its actions remain to be elucidated. The available evidence suggests that APP interacts both intracellularly and extracellularly to regulate various signal transduction mechanisms.

     

The genomic structure of two ancestral haplotypes carrying C4A duplications

Two major histocompatibility complex (MHC) ancestral haplotypes (AH) HLA A24, Bw52, C2C, BfS, C4A3 + 2, C4BQO, DRw15, DQw6 (52.1) and HLA A24, Cw7, B7, C2C, BfS, C4A3 + 3, C4B1, DR1, DQw5 (7.2), which occur with the haplotype frequencies of approximately 10% and 4% respectively in the Japanese population, carry duplicated C4A alleles by C4 allotyping. Southern blot analysis with Taq I indicated that the 52.1 AH has two C4 genes defined by 7.0 kilobase (kb) and 6.0 kb C4 hybridizing fragments but both encode C4A allotypes, being C4A3 and C4A2 respectively. The 7.2 AH carries two C4A3 and one C4B1 alleles and restriction lenght polymorphism (RFLP) analysis with Taq I showed that 6.0 kb and 7.0 kb fragments are in the proportion of 2:1. By pulsed field gel electrophoresis (PFGE) analysis, the lengths of the Pvul fragments carrying C4 and Cyp21 genes were approximately 390 kb for 52.1 and 440 kb to 7.2. The results indicate that the RFLP markers do not correlate with C4 isotype (A or B) or allotype and that the C4 gene copy number is a function of the number of genomic blocks containing C4 and Cyp21.     

Family studies of IgA deficiency

Seventeen immunoglobulin A (IgA)-deficient subjects and other members from 13 families were examined at HLA-A, B and DR, C4A, C4B, and Bf loci. Of the 29 independent haplotypes in the IgA-deficient: subjects, 22 included deletions, duplications, or defects at the C4 or 21-hydroxylase loci. It is suggested that there may be a gene regulating serum IgA concentrations in this same region of chromosome 6. Three main supratypes explain most of the previously reported tHLA associations with IgA deficiency. These are A1, Cw7, B8, C4AQ0, C4B1, BfS, DR3, Bw65(14), C4A2, C4B1/2, BfS, and Bw57(17), C4A6, C4B1, BfS. All three are proposed to carry a gene for IgA deficiency, while other supratypes carrying the same B allele generally do not. Other supratypes possibly associated with IgA deficiency were also identified. A survey of about 150 individuals with at least 1 of the 3 main supratypes revealed only 2 IgA-deficient subjects, and these were among the 20 that had 2 of these supratypes. This suggests the possibility of a recessive mode of inheritance, with penetrance determined by another factor which is not major histocompatibility complex-linked. All the supratypes found in this group of IgA-deficient subjects would then carry the putative recessive allele for IgA deficiency.     

Different allotypes of C3 degrade at different rates

To determine whether different forms of C3 degrade at different rates, we compared two strains of mice with a B10 background. The only difference was that one is C3A, while the other is OR These strains allow comparison of C3A and C3B without the added complication of differing C3 convertases. Sera from the two strains were incubated with zymosan and the degradation products were detected by immunofixation following electrophoresis in agarose. The rate of degradation of mouse C3B was more rapid than that of C3A. Differences in the rates of degradation could not be explained by differing concentrations of C3. We suggest that the genetic differences in C3 determine the decay rate following activation via the alternate pathway.     

Immunoglobulin Deposition in Liver of Patients with Active Chronic Hepatitis and Antibody against Smooth Muscle

Liver biopsies from 33 patients with miscellaneous liver diseases were studied by direct immunofluorescence. Three patients with active chronic hepatitis possessed a distinctive pattern of staining with anti-IgG conjugate. They were relatively young women and all three possessed the anti-smooth-muscle antibody. In addition, all three were untreated at the time of study. It is suggested that direct immunofluorescence on liver biopsies may help in the investigation of liver disease and that humoral immunity may participate in the pathogenesis of active chronic hepatitis.     

Dispelling myths about rare disease registry system development

Rare disease registries (RDRs) are an essential tool to improve knowledge and monitor interventions for rare diseases. If designed appropriately, patient and disease related information captured within them can become the cornerstone for effective diagnosis and new therapies. Surprisingly however, registries possess a diverse range of functionality, operate in different, often-times incompatible, software environments and serve various, and sometimes incongruous, purposes. Given the ambitious goals of the International Rare Diseases Research Consortium (IRDiRC) by 2020 and beyond, RDRs must be designed with the agility to evolve and efficiently interoperate in an ever changing rare disease landscape, as well as to cater for rapid changes in Information Communication Technologies. In this paper, we contend that RDR requirements will also evolve in response to a number of factors such as changing disease definitions and diagnostic criteria, the requirement to integrate patient/disease information from advances in either biotechnology and/or phenotypying approaches, as well as the need to adapt dynamically to security and privacy concerns. We dispel a number of myths in RDR development, outline key criteria for robust and sustainable RDR implementation and introduce the concept of a RDR Checklist to guide future RDR development.