Reduced Retinal Pigment Epithelial Autophagy Due to Loss of Rab12 Prenylation in a Human iPSC-RPE Model of Choroideremia.

Choroideremia is an X-linked chorioretinal dystrophy caused by mutations in , encoding Rab escort protein 1 (REP-1), leading to under-prenylation of Rab GTPases (Rabs). Despite ubiquitous expression of , the phenotype is limited to degeneration of the retina, retinal pigment epithelium (RPE), and choroid, with evidence for primary pathology in RPE cells. However, the spectrum of under-prenylated Rabs in RPE cells and how they contribute to RPE dysfunction remain unknown.

Immunological Features with DNA Microsatellite Alterations in Patients with Colorectal Cancer.

Competent human DNA mismatch repair (MMR) corrects DNA polymerase mistakes made during cell replication to maintain complete DNA fidelity in daughter cells; faulty DNA MMR occurs in the setting of inflammation and neoplasia, creating base substitutions (e.g. point mutations) and frameshift mutations at DNA microsatellite sequences in progeny cells.

Tetranucleotide Microsatellite Mutational Behavior Assessed in Real Time: Implications for Future Microsatellite Panels.

Background & Aims: Fifty percent of colorectal cancers show elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) and are associated with inflammation, metastasis, and poor patient outcome. EMAST results from interleukin 6-induced nuclear-to-cytosolic displacement of the DNA mismatch repair protein Mutated S Homolog 3, allowing frameshifts of dinucleotide and tetranucleotide but not mononucleotide microsatellites. Unlike mononucleotide frameshifts that universally shorten in length, we previously observed expansion and contraction frameshifts at tetranucleotide sequences.

Functional analysis of candidate genes in 2q13 deletion syndrome implicates FBLN7 and TMEM87B deficiency in congenital heart defects and FBLN7 in craniofacial malformations.

Recurrent 2q13 deletion syndrome is associated with incompletely penetrant severe cardiac defects and craniofacial anomalies. We used an atypical, overlapping 1.34 Mb 2q13 deletion in a patient with pathogenically similar congenital heart defects (CHD) to narrow the putative critical region for CHD to 474 kb containing six genes.

Membrane-myofibril cross-talk in myofibrillogenesis and in muscular dystrophy pathogenesis: lessons from the zebrafish.

Striated muscle has a highly ordered structure in which specialized domains of the cell membrane involved in force transmission (costameres) and excitation-contraction coupling (T tubules) as well as the internal membranes of the sarcoplasmic reticulum are organized over specific regions of the sarcomere. Optimal muscle function is dependent on this high level of organization but how it established and maintained is not well understood. Due to its ex utero development and transparency, the zebrafish embryo is an excellent vertebrate model for the study of dynamic relationships both within and between cells during development.

Obscurin depletion impairs organization of skeletal muscle in developing zebrafish embryos.

During development, skeletal myoblasts differentiate into myocytes and skeletal myotubes with mature contractile structures that are precisely oriented with respect to surrounding cells and tissues. Establishment of this highly ordered structure requires reciprocal interactions between the differentiating myocytes and the surrounding extracellular matrix to form correctly positioned and well-organized attachments from the skeletal muscle to the bony skeleton. Using the developing zebrafish embryo as a model, we examined the relationship between new myofibril assembly and the organization of the membrane domains involved in cell-extracellular matrix interactions.

Targeted deletion of the zebrafish obscurin A RhoGEF domain affects heart, skeletal muscle and brain development.

Obscurin is a giant structural and signaling protein that participates in the assembly and structural integrity of striated myofibrils. Previous work has examined the physical interactions between obscurin and other cytoskeletal elements but its in vivo role in cell signaling, including the functions of its RhoGTPase Exchange Factor (RhoGEF) domain have not been characterized. In this study, morpholino antisense oligonucleotides were used to create an in-frame deletion of the active site of the obscurin A RhoGEF domain in order to examine its functions in zebrafish development.

Developmental expression and differential cellular localization of obscurin and obscurin-associated kinase in cardiac muscle cells.

Obscurin and obscurin-associated kinase are two products of the obscurin transcriptional unit that encodes a recently identified giant muscle-specific protein obscurin. In this study, we characterized the developmental expression and cellular localization of obscurin and obscurin-associated kinase in cardiac muscle cells. We cloned murine obscurin-associated kinase and found that it is abundantly expressed in the heart as two isotypes encoded by 2.

Obscurin-like 1, OBSL1, is a novel cytoskeletal protein related to obscurin.

Cytoskeletal adaptor proteins serve vital functions in linking the internal cytoskeleton of cells to the cell membrane, particularly at sites of cell-cell and cell-matrix interactions. The importance of these adaptors to the structural integrity of the cell is evident from the number of clinical disease states attributable to defects in these networks. In the heart, defects in the cytoskeletal support system that surrounds and supports the myofibril result in dilated cardiomyopathy and congestive heart failure.

Obscurin is required for the lateral alignment of striated myofibrils in zebrafish.

Obscurin/obscurin-MLCK is a giant sarcomere-associated protein with multiple isoforms whose interactions with titin and small ankyrin-1 suggest that it has an important role in myofibril assembly, structural support, and the sarcomeric alignment of the sarcoplasmic reticulum. In this study, we characterized the zebrafish orthologue of obscurin and examined its role in striated myofibril assembly. Zebrafish obscurin was expressed in the somites and central nervous system by 24 hours post-fertilization (hpf) and in the heart by 48 hpf.

Orthologous relationship of obscurin and Unc-89: phylogeny of a novel family of tandem myosin light chain kinases.

Myosin light chain kinases (MLCK) are a family of signaling proteins that are required for cytoskeletal remodeling in myocytes. Recently, two novel MLCK proteins, SPEG and obscurin-MLCK, were identified with the unique feature of two tandemly-arranged MLCK domains. In this study, the evolutionary origins of this MLCK subfamily were traced to a probable orthologue of obscurin-MLCK in Drosophila melanogaster, Drosophila Unc-89, and the MLCK kinase domains of zebrafish SPEG, zebrafish obscurin-MLCK, and human SPEG were characterized.

Rapid response of cardiac obscurin gene cluster to aortic stenosis: differential activation of Rho-GEF and MLCK and involvement in hypertrophic growth.

Obscurin and obscurin myosin light chain kinase (MLCK) are two recently identified muscle proteins encoded by the same gene cluster. The production of obscurin, which contains a Rho-guanine exchange factor (GEF)-like sequence, and obscurin-MLCK by this cluster suggests that these novel genes may be involved in signal transduction cascades that control adaptive and compensatory responses of the heart. The goal of the present study was to investigate the transcriptional response of the obscurin gene cluster to the initiation of myocardial hypertrophy induced in mice by aortic constriction.

Identification, tissue expression and chromosomal localization of human Obscurin-MLCK, a member of the titin and Dbl families of myosin light chain kinases.

Members of the Dbl family of guanine nucleotide exchange factors (GEFs) have important roles in the organization of actin-based cytoskeletal structures of a wide variety of cell types. Through the activation of members of the Rho family of GTP signaling molecules, these exchange factors elicit cytoskeletal alterations that allow cellular remodeling. As important regulators of RhoGTPase activity, members of this family are candidates for mediating the RhoGTPase activation and cytoskeletal changes that occur during cardiac development and during the myocardial response to hypertrophic stimuli.