Is epigenome editing non-inheritable? Implications for ethics and the regulation of human applications.

Epigenome editing offers ethical advantages with non-inheritable gene expression control. However, concerns arise regarding potential transgenerational effects in humans. Ethical and regulatory evaluation is crucial, considering recent advancements and enhanced understanding of transgenerational epigenetics in both mammals and humans.

Characterization of hiPSC-Derived Muscle Progenitors Reveals Distinctive Markers for Myogenic Cell Purification Toward Cell Therapy.

The transplantation of muscle progenitor cells (MuPCs) differentiated from human induced pluripotent stem cells (hiPSCs) is a promising approach for treating skeletal muscle diseases such as Duchenne muscular dystrophy (DMD). However, proper purification of the MuPCs before transplantation is essential for clinical application. Here, by using MYF5 hiPSC reporter lines, we identified two markers for myogenic cell purification: CDH13, which purified most of the myogenic cells, and FGFR4, which purified a subset of MuPCs. Cells purified with each of the markers showed high efficiency for regeneration after transplantation and contributed to the restoration of dystrophin expression in DMD-immunodeficient model mice. Moreover, we found that MYF5 regulates CDH13 expression by binding to the promoter regions. These findings suggest that FGFR4 and CDH13 are strong candidates for the purification of hiPSC-derived MuPCs for therapeutical application.

Nanopore direct RNA sequencing detects DUX4-activated repeats and isoforms in human muscle cells.

Facioscapulohumeral muscular dystrophy (FSHD) is an inherited muscle disease caused by misexpression of the DUX4 gene in skeletal muscle. DUX4 is a transcription factor, which is normally expressed in the cleavage-stage embryo and regulates gene expression involved in early embryonic development. Recent studies revealed that DUX4 also activates the transcription of repetitive elements such as endogenous retroviruses (ERVs), mammalian apparent long terminal repeat (LTR)-retrotransposons and pericentromeric satellite repeats (Human Satellite II). DUX4-bound ERV sequences also create alternative promoters for genes or long non-coding RNAs, producing fusion transcripts. To further understand transcriptional regulation by DUX4, we performed nanopore long-read direct RNA sequencing (dRNA-seq) of human muscle cells induced by DUX4, because long reads show whole isoforms with greater confidence. We successfully detected differential expression of known DUX4-induced genes and discovered 61 differentially expressed repeat loci, which are near DUX4-ChIP peaks. We also identified 247 gene-ERV fusion transcripts, of which 216 were not reported previously. In addition, long-read dRNA-seq clearly shows that RNA splicing is a common event in DUX4-activated ERV transcripts. Long-read analysis showed non-LTR transposons including Alu elements are also transcribed from LTRs. Our findings revealed further complexity of DUX4-induced ERV transcripts. This catalogue of DUX4-activated repetitive elements may provide useful information to elucidate the pathology of FSHD. Also, our results indicate that nanopore dRNA-seq has complementary strengths to conventional short-read complementary DNA sequencing.

Generation of a transgene-free iPSC line and genetically modified line from a facioscapulohumeral muscular dystrophy type 2 (FSHD2) patient with SMCHD1 p.Lys607Ter mutation.

Facioscapulohumeral muscular dystrophy type2 (FSHD2), which constitutes approximately 5% of total FSHD cases and develops the same symptoms as FSHD type 1 (FSHD1), is caused by various mutations in genes including SMCHD1. We report the generation and characterization of an iPSC line derived from an FSHD2 patient carrying the SMCHD1 p.Lys607Ter mutation and its gene-corrected iPSC line which are free from transgene. These iPSC lines maintained normal karyotype, presented typical morphology, expressed endogenous pluripotency markers, and could be differentiated into ectodermal, mesodermal and endodermal cells, confirming their pluripotency.

A patient-derived iPSC model revealed oxidative stress increases facioscapulohumeral muscular dystrophy-causative DUX4.

Double homeobox 4 (DUX4), the causative gene of facioscapulohumeral muscular dystrophy (FSHD), is ectopically expressed in the skeletal muscle cells of FSHD patients because of chromatin relaxation at 4q35. The diminished heterochromatic state at 4q35 is caused by either large genome contractions [FSHD type 1 (FSHD1)] or mutations in genes encoding chromatin regulators, such as SMCHD1 [FSHD type 2 (FSHD2)]. However, the mechanism by which DUX4 expression is regulated remains largely unknown. Here, using a myocyte model developed from patient-derived induced pluripotent stem cells, we determined that DUX4 expression was increased by oxidative stress (OS), a common environmental stress in skeletal muscle, in both FSHD1 and FSHD2 myocytes. We generated FSHD2-derived isogenic control clones with SMCHD1 mutation corrected by clustered regularly interspaced short palindromic repeats (CRISPR)/ CRISPR associated 9 (Cas9) and homologous recombination and found in the myocytes obtained from these clones that DUX4 basal expression and the OS-induced upregulation were markedly suppressed due to an increase in the heterochromatic state at 4q35. We further found that DNA damage response (DDR) was involved in OS-induced DUX4 increase and identified ataxia-telangiectasia mutated, a DDR regulator, as a mediator of this effect. Our results suggest that the relaxed chromatin state in FSHD muscle cells permits aberrant access of OS-induced DDR signaling, thus increasing DUX4 expression. These results suggest OS could represent an environmental risk factor that promotes FSHD progression.