Failure of the H2 antagonist cimetidine to reverse parasite antigen-specific lymphocyte unresponsiveness in experimental filariasis.

Using sera from 75 healthy donors, 68 rheumatoid arthritis (RA) patients, and 85 tuberculosis (TB) patients, we have examined the level of antibody of the three major classes binding to seven mycobacterial species, and to three control antigens. The major findings are that IgM binding to mycobacteria is reduced in RA patients who have HLA-DR7 (P = 0.008 for M. tuberculosis antigen), and that IgA binding to mycobacteria is reduced in RA patients who have HLA-DR2 (P = 0.007 for M. tuberculosis; P = 0.0004 for M. nonchromogenicum). These associations were not seen in TB, and were restricted to these antibody isotypes. We believe this is the first report of isotype specific Class II MHC-associated regulation of antibody levels in man. A possible interpretation of our data is that patients bearing these haplotypes are recognizing suppressor epitopes common to all the mycobacterial species tested. Since DR2 and DR7 have recently been shown to be associated with a significantly reduced risk of RA, our findings are compatible with the view that changes in immune responsiveness to mycobacterial antigens, or to autoantigens which cross-react with them, are relevant to RA.     

doublecortin is the major gene causing X-linked subcortical laminar heterotopia (SCLH)

Subcortical laminar heterotopia (SCLH), or 'double cortex', is a cortical dysgenesis disorder associated with a defect in neuronal migration. Clinical manifestations are epilepsy and mental retardation. This disorder, which mainly affects females, can be inherited in a single pedigree with lissencephaly, a more severe disease which affects the male individuals. This clinical entity has been described as X- SCLH/LIS syndrome. Recently we have demonstrated that the doublecortin gene, which is localized on the X chromosome, is implicated in this disorder. We have now performed a systematic mutation analysis of doublecortin in 11 unrelated females with SCLH (one familial and 10 sporadic cases) and have identified mutations in 10/11 cases. The sequence differences include nonsense, splice site and missense mutations and these were found throughout the gene. These results provide strong evidence that loss of function of doublecortin is the major cause of SCLH. The absence of phenotype-genotype correlations suggests that X-inactivation patterns of neuronal precursor cells are likely to contribute to the variable clinical severity of this disorder in females.      

Incomplete rescue of cystic fibrosis transmembrane conductance regulator deficient mice by the human CFTR cDNA

We have used a mouse model to study the ability of human CFTR to correct the defect in mice deficient of the endogenous protein. In this model, expression of the endogenous Cftr gene was disrupted and replaced with a human CFTR cDNA by a gene targeted 'knock-in' event. Animals homozygous for the gene replacement failed to show neither improved intestinal pathology nor survival when compared to mice completely lacking CFTR. RNA analyses showed that the human CFTR sequence was transcribed from the targeted allele in the respiratory and intestinal epithelial cells. Furthermore, in vivo potential difference measurements showed that basal CFTR chloride channel activity was present in the apical membranes of both nasal and rectal epithelial cells in all homozygous knock-in animals examined. Ussing chamber studies showed, however, that the cAMP-mediated chloride channel function was impaired in the intestinal tract among the majority of homozygous knock-in animals. Hence, failure to correct the intestinal pathology associated with loss of endogenous CFTR was related to inefficient functional expression of the human protein in mice. These results emphasize the need to understand the tissue- specific expression and regulation of CFTR function when animal models are used in gene therapy studies.      

Successful outcome with day 4 embryo transfer after preimplantation diagnosis for genetically transmitted diseases

Preimplantation genetic diagnosis was performed in 61 day 3 embryos obtained by in-vitro fertilization from seven patient carriers of haemophilia, Marfan's syndrome, Bloch-Sulzemberg syndrome (incontinentia pigmentosa) or X chromosome-linked immune deficiency, retinitis pigmentosa, and FG syndrome, which is characterized by mental retardation and hypotonia. After multiplex polymerase chain reaction, 16 embryos were diagnosed as being unaffected, and these were transferred to the uterus on the following day (day 4). Of these embryos, six (37.5%) implanted, resulting in the delivery of a singleton and a twin pregnancy, a late second trimester miscarriage (twins at week 20) and a first trimester miscarriage at week 8. All the diagnoses were confirmed by amniocentesis. We report for the first time a late day 4 transfer of biopsied human embryos undergoing preimplantation genetic diagnosis. This transfer schedule allows an extra day to perform genetic analyses on single blastomeres and to monitor any adverse effect of the biopsy procedure.      

Hereditary Cerebral Hemorrhage with Amyloidosis-Dutch Type (HCHWA-D): I - A Review of Clinical, Radiologic and Genetic Aspects

Hereditary cerebral hemorrhage with amyloidosis - Dutch type (HCHWA-D) is an autosomal dominant disease caused by deposition of β-amyloid in the leptomeningeal arteries and cortical arterioles, in addition to preamyloid deposits and amyloid plaques in the brain parenchyma.
The disease is due to a point mutation at codon 693 of the amyloid precursor protein (βPP) gene at chromosome 21. Since this point mutation is diagnostic for HCHWA-D, presymptomatic testing is feasible and offered, together with genetic counselling and psychological support, to subjects at risk. HCHWA-D is clinically characterized by recurrent strokes, in addition to dementia, which can occur after the first stroke but also preceding it. Radiological studies revealed focal lesions (hemorrhages, hemorrhagic and non-hemorrhagic infarctions) and diffuse white matter damage. Diffuse white matter hyperintensities on MRI are an early symptom of HCHWA-D since they have been found on MRI scans of subjects who had not suffered a stroke.
The presence of the diagnostic point mutation makes HCHWA-D a useful model to study the effects of cerebral amyloid angiopathy in vivo. The characteristic pathological abnormalities and its implications for Alzheimer's disease will be discussed in Part II of this article