2.1 kb 5'-flanking region of the brain type dystrophin gene directs the expression of lacZ in the cerebral cortex, but not in the hippocampus

Novel mutation in splicing donor of dystrophin gene first exon in a patient with dilated cardiomyopathy but no clinical signs of skeletal myopathy

One cause of X-linked dilated cardiomyopathies is mutation of the dystrophin gene. We report the case of a young boy who suffered from dilated cardiomyopathy caused only by dystrophin-deficient cardiac muscle, but who did not present with any clinical signs of skeletal myopathy. Sequence analysis of the patient's dystrophin gene revealed the presence of a novel single point mutation at the first exon-intron boundary, inactivating the 5' splice site consensus sequence of the first intron. The lack of muscle weakness observed clinically can be explained by expression of the brain and Purkinje dystrophin isoforms in skeletal muscle.

Structural diversity despite strong evolutionary conservation in the 5'-untranslated region of the P-type dystrophin transcript

Analysis of the 5'-flanking regions of the Purkinje (P-) dystrophin genes and mRNAs in different species revealed strong sequence conservation but functional diversity. Multiple transcription initiation sites were identified in cerebella and muscles, tissues expressing P-dystrophin. The predominant initiation site was conserved, with another muscle-specific site located upstream. Despite sequence homology, significant tissue- and species-specific structural diversity in the P-type 5'-ends exists, including alternative splicing within the 5'-untranslated region combined with alternative splicing of intron 1. One amino terminus is conserved in mammals and, to a lesser extent, in chicken. However, alternative usage of ATG codons may result in a choice of N-termini or translation of short upstream ORFs in different species. Promoter activity of a fragment upstream of the cap site was shown by transient expression in myoblasts and in vivo following intramuscular injection. It is tissue- and developmentally regulated. Analysis of promoter deletions suggests the existence of negative regulatory elements in the proximal region.

Poor verbal working memory across intellectual level in boys with Duchenne dystrophy

OBJECTIVE

To determine whether all boys with Duchenne muscular dystrophy (DMD) have a similar verbal and memory profile of skills, or whether only a subset is affected, and to determine whether the weak areas in their profile are substantially different from a control group.

METHODS

Performance of patients with DMD on neuropsychological tests of verbal and memory skills was examined in two ways. Standardized test scores for 80 boys with DMD (estimated IQ range, 70 to 160) were ranked individually from worst to best, and the individual rankings were compared across the group using Friedman rank analysis. Additionally, performance of 41 boys with DMD was compared with that of their sibling control subjects of similar age and estimated IQ using multivariate analysis of variance.

RESULTS

Individual cognitive profiles were significantly similar among the subjects with DMD, such that for most subjects digit span, story recall, and comprehension were the tests on which each performed most poorly. This finding remained true regardless of whether they were of high or low intellectual function. In contrast, no significant cognitive profile was found among their sibling control subjects, and when compared with their siblings, the DMD group scored significantly more poorly on digit span, comprehension, and story recall, but not on other verbal and memory measures.

CONCLUSIONS

Boys with DMD have a specific cognitive profile, regardless of their general level of cognitive function. Specifically, boys with DMD performed more poorly on tests requiring attention to complex verbal information than they did on other verbal or memory measures. The possibility that the missing dystrophin brain products may contribute to selective cognitive processing is considered.

Expression analysis of Escherichia coli lacZ reporter gene in transgenic mice

To define a gene expression mechanism, it is often advantageous to use a reporter gene and transgenic mouse. The lacZ reporter gene is particularly useful for studies of the cis-regulatory element for tissue-specific expression in transgenic mice because of the ease of the enzyme assay and visualization on sections. In this report, we describe our method for examining the cis-regulatory element in transgenic mice, including choice of the lacZ gene, generation of transgenic mice, and analysis of beta-galactosidase activity.

Brain dystrophin, neurogenetics and mental retardation

Duchenne muscular dystrophy (DMD) and the allelic disorder Becker muscular dystrophy (BMD) are common X-linked recessive neuromuscular disorders that are associated with a spectrum of genetically based developmental cognitive and behavioral disabilities. Seven promoters scattered throughout the huge DMD/BMD gene locus normally code for distinct isoforms of the gene product, dystrophin, that exhibit nervous system developmental, regional and cell-type specificity. Dystrophin is a complex plasmalemmal-cytoskeletal linker protein that possesses multiple functional domains, autosomal and X-linked homologs and associated binding proteins that form multiunit signaling complexes whose composition is unique to each cellular and developmental context. Through additional interactions with a variety of proteins of the extracellular matrix, plasma membrane, cytoskeleton and distinct intracellular compartments, brain dystrophin acquires the capability to participate in the modulatory actions of a large number of cellular signaling pathways. During neural development, dystrophin is expressed within the neural tube and selected areas of the embryonic and postnatal neuraxis, and may regulate distinct aspects of neurogenesis, neuronal migration and cellular differentiation. By contrast, in the mature brain, dystrophin is preferentially expressed by specific regional neuronal subpopulations within proximal somadendritic microdomains associated with synaptic terminal membranes. Increasing experimental evidence suggests that in adult life, dystrophin normally modulates synaptic terminal integrity, distinct forms of synaptic plasticity and regional cellular signal integration. At a systems level, dystrophin may regulate essential components of an integrated sensorimotor attentional network. Dystrophin deficiency in DMD/BMD patients and in the mdx mouse model appears to impair intracellular calcium homeostasis and to disrupt multiple protein-protein interactions that normally promote information transfer and signal integration from the extracellular environment to the nucleus within regulated microdomains. In DMD/BMD, the individual profiles of cognitive and behavioral deficits, mental retardation and other phenotypic variations appear to depend on complex profiles of transcriptional regulation associated with individual dystrophin mutations that result in the corresponding presence or absence of individual brain dystrophin isoforms that normally exhibit developmental, regional and cell-type-specific expression and functional regulation. This composite experimental model will allow fine-level mapping of cognitive-neurogenetic associations that encompass the interrelationships between molecular, cellular and systems levels of signal integration, and will further our understanding of complex gene-environmental interactions and the pathogenetic basis of developmental disorders associated with mental retardation.

Functional dissection of the cytoplasmic subregions of the IL-2 receptor betac chain in primary lymphocyte populations

The interleukin 2 (IL-2) receptor betac chain (IL-2Rbetac) is known to regulate the development and function of distinct lymphocyte populations. Thus far, the functions of the IL-2Rbetac cytoplasmic subregions have been studied extensively by using cultured cell lines; however, this approach has limitations with respect to their functions in distinct primary lymphocyte populations. In the present study, we generated mice each expressing a mutant form of an IL-2Rbetac transgene, lacking the cytoplasmic A- or H-region, on an IL-2Rbetac null background. We show that lack of the H-region, which mediates activation of the Stat5/Stat3 transcription factors, selectively affects the development of natural killer cells and T cells bearing the gamma delta T cell receptor. This region is also required for the IL-2-induced proliferation of T cells in vitro, by upregulating IL-2Ralpha expression. In contrast, the A-region, which mediates activation of the Src family protein tyrosine kinase (PTK) members, contributes to downregulation of the T cell proliferation function. The IL-2Rbetac null mutant mice develop severe autoimmune symptoms; these are all suppressed following the expression of either of the mutants, suggesting that neither the Stats nor the Src PTK members are required. Thus, our present approach offers new insights into the functions of these cytoplasmic subregions of the IL-2Rbetac chain.

lacZ transgenic mice to monitor gene expression in embryo and adult

In transgenic experiments, lacZ can be used as a reporter gene for activity of a given promoter. Its main advantage is the ease of visualization in situ, on sections or in whole mount preparations, and the availability of simple protocols. In the following, we describe our procedure for detecting promoter activity in transgenic mice, including choice of lacZ vectors, generation of the transgenic mice, and analysis of expression. We had recently used this protocol to detect tyrosinase gene promoter activity in embryonic and adult brain.