The Ufm1 system is upregulated by ER stress during osteogenic differentiation

ObjectiveMutations in the catalytic site of the ubiquitin-fold modifier 1(UFM1)-specific peptidase 2 (UFSP2) gene have been identified to cause autosomal dominant Beukes hip dysplasia in a large multigenerational family and a novel form of autosomal dominant spondyloepimetaphyseal dysplasia in a second family. We investigated the expression of the UFSP2/UFM1 system during mouse joint development the connection to ER stress induced during osteogenic differentiation.MethodsThe pattern of expression of Ufsp2 was determined by radioactive RNA in situ hybridisation on mouse tissue sections. qPCR was used to monitor expression during in vitro osteogenic differentiation and chemically induced ER stress. Affinity purification and mass spectrometry was used for isolation and identification of Ufm1 conjugation targets. Luciferase reporter assay was used to investigate the activity of Ufm1 system genes’ promoters.ResultsWe found that Ufsp2 was predominantly expressed in the bone and secondary ossification centres of 10-day old mice. The Ufm1 system was upregulated during in vitro osteogenic differentiation and in response to chemically induced ER stress. We identified unfolded protein response elements in the upstream sequences of Uba5, Ufl1, Ufm1and Lzap. We identified putative Ufm1 conjugation targets where conjugation was increased in response to ER stress.ConclusionHigher expression of Ufsp2 in bone and secondary ossification centres as well as upregulation of components of the Ufm1system in response to ER stress suggests that the molecular pathway between the UFSP2 mutations and form of skeletal dysplasia may relate to abnormal ER stress responses during osteoblast differentiation.

Gender differences in the order of appearance of elbow ossification centres

Background The predictable order of appearance of elbow secondary ossification centres in children is important in interpreting elbow radiographs, most commonly in the context of trauma. The usual sequence of appearance of these ossification centres is given by the acronym CRITOL, but exceptions have been described and are recognised as normal variants. Aim To investigate the extent to which the appearance of the elbow secondary ossification centres follows a predictable sequence, and to establish the incidence of exceptions to the usual CRITOL order. Methods Two-stage retrospective review of 421 elbow radiographs in children at our centre. Results Of 64 children with two visible ossification centres, there was a 23% overall variant incidence (49 CR, 15 CI). Twenty-eight children had four visible ossification centres, with an overall variant incidence of 32% (19 CRIT, 9 CRIO). The variants were significantly more common in girls than in boys ( p < 0.001). Conclusion Whilst the majority of radiographs remained consistent with the described CRITOL sequence, variance in this order was seen in a quarter of children with two visible ossification centres, and a third of children with four visible ossification centres. Incidence of variance was much more common in girls, reaching statistical significance. Awareness of these normal variations, particularly in girls, should help to avoid misinterpretation.

Radiographic and computed tomographic assessment of the development of the antebrachia and elbow joints in Labrador Retrievers with and without medial coronoid disease

SummaryObjectives: To compare the development, monitored by radiography and computed tomography, of the antebrachia and elbow joints in seven Labrador Retrievers with healthy elbow joints and in seven Labrador Retrievers that developed medial coronoid disease (MCD), in order to determine whether disturbances in the development of the antebrachia and elbow joints, between the age of six and 17 weeks may lead to medial coronoid disease.Methods: A prospective study of 14 Labrador Retrievers in their active growth stage was performed. The development of the antebrachia and elbow joints was assessed between six and 17 weeks of age using radio graphy and computed tomography determining the development of secondary ossification centres, radioulnar length ratio, radial angulation, and inter-relationship between the humerus, ulna and radius.Results: For the parameters of ossification of secondary ossification centres, radioulnar length ratio, radial angulation, and joint congruence evaluation, there was no significant difference in the development of the ante-brachia and elbow joints of seven Labrador Retrievers positive and seven Labrador Retrievers negative for MCD at the age of six to 17 weeks.Clinical significance: These findings demonstrate that the development of MCD in the Labrador Retrievers in our study was not related to any disturbance in the development of the antebrachia and elbow joints during the rapid growth phase.