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Articles by M. D Schneider
Total Records ( 2 ) for M. D Schneider
  X Ma , K Takeda , A Singh , Z. X Yu , P Zerfas , A Blount , C Liu , J. A Towbin , M. D Schneider , R. S Adelstein and Q. Wei

Rationale: Germline ablation of the cytoskeletal protein nonmuscle myosin II (NMII)-B results in embryonic lethality, with defects in both the brain and heart. Tissue-specific ablation of NMII-B by a Cre recombinase strategy should prevent embryonic lethality and permit study of the function of NMII-B in adult hearts.

Objective: We sought to understand the function of NMII-B in adult mouse hearts and to see whether the brain defects found in germline-ablated mice influence cardiac development.

Methods and Results: We used a loxP/Cre recombinase strategy to specifically ablate NMII-B in the brains or hearts of mice. Mice ablated for NMII-B in neural tissues die between postnatal day 12 and 22 without showing cardiac defects. Mice deficient in NMII-B only in cardiac myocytes (BMHC/BMHC mice) do not show brain defects. However, BMHC/BMHC mice display novel cardiac defects not seen in NMII-B germline-ablated mice. Most of the BMHC/BMHC mice are born with enlarged cardiac myocytes, some of which are multinucleated, reflecting a defect in cytokinesis. Between 6 to 10 months, they develop a cardiomyopathy that includes interstitial fibrosis and infiltration of the myocardium and pericardium with inflammatory cells. Four of 5 BMHC/BMHC hearts develop marked widening of intercalated discs.

Conclusions: By avoiding the embryonic lethality found in germline-ablated mice, we were able to study the function of NMII-B in adult mice and show that absence of NMII-B in cardiac myocytes results in cardiomyopathy in the adult heart. We also define a role for NMII-B in maintaining the integrity of intercalated discs.

  K Hidaka , M Shirai , J. K Lee , T Wakayama , I Kodama , M. D Schneider and T. Morisaki

Rationale: The paucity of specific surface markers for cardiomyocytes and their progenitors has impeded the development of embryonic or pluripotent stem cell–based transplantation therapy. Identification of relevant surface markers may also enhance our understanding of the mechanisms underlying differentiation.

Objective: Here, we show that cellular prion protein (PrP) serves as an effective surface marker for isolating nascent cardiomyocytes as well as cardiomyogenic progenitors.

Methods and Results: Embryonic stem (or embryo-derived) cells were analyzed using flow cytometry to detect surface expression of PrP and intracellular myosin heavy chain (Myhc) proteins. Sorted cells were then analyzed for their differentiation potential.

Conclusions: PrP+ cells from beating embryoid bodies (EBs) frequently included nascent Myhc+ cardiomyocytes. Cultured PrP+ cells further differentiated, giving rise to cardiac troponin I+ definitive cardiomyocytes with either an atrial or a ventricular identity. These cells were electrophysiologically functional and able to survive in vivo after transplantation. Combining PrP with a second marker, platelet-derived growth factor receptor (PDGFR), enabled us to identify an earlier cardiomyogenic population from prebeating EBs, the PrP+PDGFR+ (PRa) cells. The Myhc PRa cells expressed cardiac transcription factors, such as Nkx2.5, T-box transcription factor 5, and Isl1 (islet LIM homeobox 1), although they were not completely committed. In mouse embryos, PRa cells in cardiac crescent at the 1 to 2 somite stage were Myhc+, whereas they were Myhc at headfold stages. PRa cells clonally expanded in methlycellulose cultures. Furthermore, single Myhc PRa cell–derived colonies contained both cardiac and smooth muscle cells. Thus, PrP demarcates a population of bipotential cardiomyogenic progenitor cells that can differentiate into cardiac or smooth muscle cells.

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