CSNK1a1 Regulates PRMT1 to Maintain the Progenitor State in Self-Renewing Somatic Tissue

Somatic progenitors sustain tissue self-renewal while suppressing premature differentiation. Protein arginine methyltransferases (PRMTs) affect many processes; however, their role in progenitor function is incompletely understood. PRMT1 was found to be the most highly expressed PRMT in epidermal progenitors and the most downregulated PRMT during differentiation. In targeted mouse knockouts and in long-term regenerated human mosaic epidermis in vivo, epidermal PRMT1 loss abolished progenitor self-renewal and led to premature differentiation. Mass spectrometry of the PRMT1 protein interactome identified the CSNK1a1 kinase, which also proved essential for progenitor maintenance. CSNK1a1 directly bound and phosphorylated PRMT1 to control its genomic targeting to PRMT1-sustained proliferation genes as well as PRMT1-suppressed differentiation genes. Among the latter were GRHL3, whose derepression was required for the premature differentiation seen with PRMT1 and CSNK1a1 loss. Maintenance of the progenitors thus requires cooperation by PRMT1 and CSNK1a1 to sustain proliferation gene expression and suppress premature differentiation driven by GRHL3.

Effect of minichromosome maintenance protein 2 deficiency on the locations of DNA replication origins

Minichromosome maintenance (MCM) proteins are loaded onto chromatin during G1-phase and define potential locations of DNA replication initiation. MCM protein deficiency results in genome instability and high rates of cancer in mouse models. Here we develop a method of nascent strand capture and release and show that MCM2 deficiency reduces DNA replication initiation in gene-rich regions of the genome. DNA structural properties are shown to correlate with sequence motifs associated with replication origins and with locations that are preferentially affected by MCM2 deficiency. Reduced nascent strand density correlates with sites of recurrent focal CNVs in tumors arising in MCM2-deficient mice, consistent with a direct relationship between sites of reduced DNA replication initiation and genetic damage. Between 10% and 90% of human tumors, depending on type, carry heterozygous loss or mutation of one or more MCM2-7 genes, which is expected to compromise DNA replication origin licensing and result in elevated rates of genome damage at a subset of gene-rich locations.

Biplanar exposure of the radius and ulna through a single incision

The surgical approaches used to expose fractures of both bones of the forearm vary depending on the site and type of fracture and the degree of comminution; all have limitations. An exposure is described which allows access to most of the radius and ulna through a single skin incision.

Isolated Radiopalmar Dislocation of Fifth Carpometacarpal Joint: A Rare Presentation

Carpometacarpal (CMC) joint dislocations are uncommon injuries that account for less than 1% of hand injuries. Dorsal dislocations of the CMC joints are more frequent than volar dislocations. Palmar dislocations can be either ulnopalmar or radiopalmar. There are very few reports of isolated radiopalmar dislocations of the fifth CMC joint in the English-language literature. In our case of radiopalmar dislocation, diagnosis was delayed, and attempts at closed reduction were unsuccessful. Therefore, it was treated by open reduction and Kirschner-wire fixation. This article reports a rare type of injury and discusses its management.