Myogenic stem cell function is impaired in mice lacking the forkhead /winged helix protein MNF

Abstract

Myocyte nuclear factor (MNF) is a winged helix transcription factor that is expressed selectively in myogenic stem cells (satellite cells) of adult animals. Using a gene knockout strategy to generate a functional null allele at the Mnf locus, we observed that mice lacking MNF are viable, but severely runted. Skeletal muscles of Mnf؊͞؊ animals are atrophic, and satellite cell function is impaired. Muscle regeneration after injury is delayed and incomplete, and the normal timing of expression of cell cycle regulators and myogenic determination genes is dysregulated. Mnf mutant mice were intercrossed with mdx mice that lack dystrophin and exhibit only a subtle myopathic phenotype. In contrast, mdx mice that also lack MNF die in the first few weeks of life with a severe myopathy. Haploinsufficiency at the Mnf locus (Mnf؉͞؊) also exacerbates the mdx phenotype to more closely resemble Duchenne's muscular dystrophy in humans. We conclude that MNF acts to regulate genes that coordinate the proliferation and differentiation of myogenic stem cells after muscle injury. Animals deficient in MNF may prove useful for evaluation of potential therapeutic interventions to promote muscle regeneration for patients having Duchenne's muscular dystrophy.

Mobilisation of satellite cells following ischaemia and reperfusion in primate skeletal muscle

“…In other models, using crushing, 27 freezing, 9 or chemically induced injuries to skeletal muscle 12 to study satellite cell activation, proliferation and regeneration, two response of satellite cells to activation have been described. These are based on the integrity of the basal lamina.…”

Absence of p21CIP Rescues Myogenic Progenitor Cell Proliferative and Regenerative Capacity in Foxk1 Null Mice

“…Primers for real-time and semiquantitative RT-PCR were: p27, For 5Ј-TTGGGTCTCAGGCAAACTC-T-3Ј; p27, Rev 5Ј-TCTGTTCTGTTGGCCCTTTT-3Ј; p53, For 5Ј-AAGT-CCTTTGCCCTGAACTG-3Ј; p53, Rev 5Ј-CTGTAGCATGGGCATCCTT-T-3Ј; p21, For 5Ј-TTGCACTCTGGTGTCTGAGC-3Ј; p21, Rev 5Ј-CTGC-GCTTGGAGTGATAGAA-3Ј; cyclin B1, For 5Ј-AACCTGAGCCTGAAC-CTGAA-3Ј, cyclin B1, Rev 5Ј-GCGTCTACGTCACTCACTGC-3Ј; cyclin D1, For 5Ј-CGGATGAGAACAAGCAGACC-3Ј; cyclin D1, Rev5Ј-GCAG-GAGAGGAAGTTGTTGG-3Ј; p57, For 5Ј-AGGAGCAGGACGAGAATC-AAG-3Ј; p57, Rev 5Ј-ACATGAACGAAAGGTCCCAG-3Ј; cdk1, For 5Ј-G-GTCCGTCGTAACCTGTTGA-3Ј; cdk1, Rev 5Ј-CTCCTTCTTCCTCGC-TTTCA-3Ј; glyceraldehyde-3-phosphate dehydrogenase, For 5Ј-GTGG-CAAAGTGGAGATTGTTGCC-3Ј; glyceraldehyde-3-phosphate dehydrogenase, Rev 5Ј-GATGATGACCCGTTTGGCTCC-3Ј. Western analysis of protein extracts isolated from wild type or Foxk1Ϫ/Ϫ progenitor cell cultures was performed as described previously using rabbit anti-p21 or rabbit anti-p53 sera (1:1000 dilution, Santa Cruz Biotechnologies) (15).…”

“…Cardiotoxin Injury of Mouse Skeletal Muscle-Gastrocnemius muscles from WT, Foxk1Ϫ/Ϫ, and Foxk1Ϫ/Ϫ:p21 CIP Ϫ/Ϫ mice (2-month-old) were injected with cardiotoxin (150 l/muscle of 10 M cardiotoxin (Naja nigricollis; Calbiochem)) (15). Muscles were harvested 10 days post-injection and fixed overnight with 4% paraformaldehyde.…”

“…We have identified a novel member of the forkhead/winged helix transcription factor family, termed Foxk1 (previously referred to as myocyte nuclear factor or MNF) (14,15). Foxk1 is expressed early, selectively, and transiently in the developing neural tube, heart, and somites of the mouse embryo.…”

Muscle stem cells and model systems for their investigation

“…Several satellite cell markers have also been identified. Among them are paired box transcription factors Pax3 and Pax7 (Seale and Rudnicki, 2000;Relaix et al, 2006); c-met, the receptor for hepatocyte growth factor (HGF; Cornelison and Wold, 1997); myocyte nuclear factor (MNF; Hawke and Garry, 2001;Garry et al, 2000); Mcadherin, a calcium-dependent cell adhesion molecule (Irintchev et al, 1994;Moore and Walsh, 1993); vascular cell adhesion molecule 1 (VCAM1; Rosen et al, 1992); neural cell adhesion molecule (N-CAM; Illa et al, 1992); CD34, a hematopoietic stem cell marker (Beauchamp et al, 2000); and heparan sulfate proteoglycans Syndecan 3 and 4 (Cornelison et al, 2001). It has been clearly demonstrated that activation, proliferation, and differentiation of satellite cells after injury are controlled by members of the myogenic regulatory factor (MRF) family, in a similar manner to muscle precursor cells during embryonic development.…”