Thymopoietin (lamina-associated polypeptide 2) gene mutation associated with dilated cardiomyopathy.

Thymopoietin or TMPO (indicated by its alternative gene symbol, LAP2, in this work) has been proposed as a candidate disease gene for dilated cardiomyopathy (DCM), since a LAP2 product associates with nucleoplasmic lamins A/C, which are encoded by the DCM gene LMNA. We developed a study to screen for genetic mutations in LAP2 in a large collection of DCM patients and families. A total of 113 subjects from 88 families (56 with familial DCM (FDC) and 32 with sporadic DCM) were screened for LAP2 mutations using denaturing high-performance liquid chromatography and sequence analysis. We found a single putative mutation affecting the LAP2alpha isoform in one FDC pedigree. The mutation predicts an Arg690Cys substitution (c.2068C>T; p.R690C) located in the C-terminal domain of the LAP2alpha protein, a region that is known to interact with lamin A/C. RT-PCR, Western blot analyses, and immunolocalization revealed low-level LAP2alpha expression in adult cardiac muscle, and localization to a subset of nuclei. Mutated Arg690Cys LAP2alpha expressed in HeLa cells localized to the nucleoplasm like wild-type LAP2alpha, with no effect on peripheral and nucleoplasmic lamin A distribution. However, the in vitro interaction of mutated LAP2alpha with the pre-lamin A C-terminus was significantly compromised compared to the wild-type protein. LAP2 mutations may represent a rare cause of DCM. The Arg690Cys mutation altered the observed LAP2alpha interaction with A-type lamins. Our finding implicates a novel nuclear lamina-associated protein in the pathogenesis of genetic forms of dilated cardiomyopathy.

Alpha-myosin heavy chain: a sarcomeric gene associated with dilated and hypertrophic phenotypes of cardiomyopathy.

BACKGROUND: Mutations in the beta-myosin heavy-chain (betaMyHC) gene cause hypertrophic (HCM) and dilated (DCM) forms of cardiomyopathy. In failing human hearts, downregulation of alphaMyHC mRNA or protein has been correlated with systolic dysfunction. We hypothesized that mutations in alphaMyHC could also lead to pleiotropic cardiac phenotypes, including HCM and DCM. METHODS AND RESULTS: A cohort of 434 subjects, 374 (134 affected, 214 unaffected, 26 unknown) belonging to 69 DCM families and 60 (29 affected, 30 unaffected, 1 unknown) in 21 HCM families, was screened for alphaMyHC gene (MYH6) mutations. Three heterozygous MYH6 missense mutations were identified in DCM probands (P830L, A1004S, and E1457K; 4.3% of probands). A Q1065H mutation was detected in 1 of 21 HCM probands and was absent in 2 unaffected offspring. All MYH6 mutations were distributed in highly conserved residues, were predicted to change the structure or chemical bonds of alphaMyHC, and were absent in at least 300 control chromosomes from an ethnically similar population. The DCM carrier phenotype was characterized by late onset, whereas the HCM phenotype was characterized by progression toward dilation, left ventricular dysfunction, and refractory heart failure. CONCLUSIONS: This study suggests that mutations in MYH6 may cause a spectrum of phenotypes ranging from DCM to HCM.

17q-linked frontotemporal dementia-amyotrophic lateral sclerosis without tau mutations with tau and alpha-synuclein inclusions.

BACKGROUND: Frontotemporal dementia (FTD) is a clinically heterogeneous condition that can be associated with clinical manifestations of an extrapyramidal disorder or motor neuron disease. A range of histologic patterns has been described in patients with FTD. The most common familial form of this condition is caused by mutations in the microtubule-associated protein tau gene (MAP tau) and is associated with neuronal or glial tau inclusions. OBJECTIVES: To determine the clinical, anatomic, and pathological features of San Francisco family A and to map the mutation responsible for disease in this family. DESIGN: A systematic clinical, neuropsychologic, neuroimaging, and chromosome segregation analysis of San Francisco family A was performed. A pathological and biochemical assessment of a family member was made. SETTING: Family study. PATIENTS: San Francisco family A, with FTD, variable extrapyramidal symptoms, and prominent motor neuron disease. Afflicted family members do not have a MAP tau coding or splice regulatory sequence mutation, and the MAP tau is genetically excluded. MAIN OUTCOME MEASURES: Comparison of clinical, neuropsychologic, neuroimaging, and linkage findings of San Francisco family A with other familial forms of FTD and amyotrophic lateral sclerosis (ALS). RESULTS: The most probable location for the mutation responsible for this condition is on chromosome arm 17q, distal to the MAP tau. All previously identified susceptibility loci for FTD and ALS are excluded. Autopsy findings from an afflicted family member show distinctive tau and alpha-synuclein inclusions. Another unique feature is that the insoluble tau protein consists predominantly of the 4R/0N isoform. CONCLUSION: The condition affecting members of San Francisco family A is clinically, pathologically, and genetically distinct from previous familial forms of FTD and ALS.

The KH-type RNA-binding protein PSI is required for Drosophila viability, male fertility, and cellular mRNA processing.

Direct interactions between RNA-binding proteins and snRNP particles modulate eukaryotic pre-mRNA processing patterns to control gene expression. Here, we report that the conserved U1 snRNP-interacting RNA-binding protein PSI is essential for Drosophila viability. A null PSI mutation is recessive lethal at the first-instar larval stage, and lethality is fully rescued by transgenes expressing the PSI protein. A mutant transgene that lacks the PSI-U1 snRNP-interaction domain restores viability but shows courtship behavior abnormalities and meiosis defects during spermatogenesis, resulting in a complete male sterility phenotype. Using cDNA microarrays, we have identified specific target mRNAs with altered expression profiles in these mutant males. A subset of these transcripts is also found associated with PSI in endogenous immunopurified ribonucleoprotein complexes. One specific target, the hrp40/squid transcript, shows an altered pre-mRNA splicing pattern in PSI mutant testes. We conclude that a functional association between the PSI protein and the spliceosomal U1 snRNP particle is required for normal Drosophila development and for the processing of specific PSI-interacting cellular transcripts. These results also validate the use of cDNA microarrays to characterize in vivo RNA-processing defects and alternative pre-mRNA splicing patterns.