Transcriptomic landscape of human induced pluripotent stem cell-derived osteogenic differentiation identifies a regulatory role of KLF16

Osteogenic differentiation is essential for bone development and metabolism, but the underlying gene regulatory networks have not been well investigated. We differentiated mesenchymal stem cells, derived from 20 human induced pluripotent stem cell lines, into preosteoblasts and osteoblasts, and performed systematic RNA-seq analyses of 60 samples for differential gene expression. We noted a highly significant correlation in expression patterns and genomic proximity among transcription factor (TF) and long noncoding RNA (lncRNA) genes. We identified TF-TF regulatory networks, regulatory roles of lncRNAs on their neighboring coding genes for TFs and splicing factors, and differential splicing of TF, lncRNA, and splicing factor genes. TF-TF regulatory and gene co-expression network analyses suggested an inhibitory role of TF KLF16 in osteogenic differentiation. We demonstrate that in vitro overexpression of human KLF16 inhibits osteogenic differentiation and mineralization, and in vivo Klf16+/- mice exhibit increased bone mineral density, trabecular number, and cortical bone area. Thus, our model system highlights the regulatory complexity of osteogenic differentiation and identifies novel osteogenic genes.

Family Studies of Patients with Reduced Ristocetin Aggregation and Abnormalities of Factor VIII and/or Platelet Function

Factor VIII procoagulant activity (VIIIc), antigen (vWa), mobility of the antigen on two dimensional Immunoelectrophoresis and platelet function were studied in 9 families with reduced ristocetin induced platelet aggregation rate (RIPA) and/or deficiency of plasma factor(s) required for ristocetin aggregation of washed normal platelets (vWf). The families could be subdivided into 4 groups. Group I showed dominant inheritance and reduced levels of VIIIc and vWa characteristic of typical von Willebrand’s disease. All patients had reduced vWf and in 7 of 10 RIPA was reduced. Group II showed normal levels of VIIIc but reduced vWa. All showed reduced vWf but RIPA was reduced in one patient only. There was a good correlation between vWf and vWa and VIIIc in both groups. The bleeding time correlated with vWf in group I but not group II. Group III showed normal or nearly normal VIIIc and vWa but there was an increased mobility of vWa compared to normals and to groups I and II. RIPA was markedly reduced as was the vWf in one patient. Group IV is represented by one child with a strong family history of bleeding, who had reduced RIPA and defective platelet release reaction. The vWf in this child was normal and the ratio between VIIIc and vWa was similar to that seen in carriers of haemophilia. This spectrum of abnormalities of ristocetin aggregation justifies the use of the term ‘von Willebrand’s syndrome’.

Ristocetin in the Diagnosis of von Willebrand’s Disease: A Comparison of Rate and Percent of Aggregation with Levels of the Plasma Factor(s) Necessary for Ristocetin Aggregation

Percent aggregation and the aggregation rate of platelet rich plasma (PRP) in response to ristocetin (1.75 mg/ml) were measured in 20 normals and 16 patients with von Willebrand’s disease (vWd), with and without the addition of acetylsalicylic acid (ASA). Percent aggregation did not clearly distinguish between normals and patients with vWd. Aggregation rate was normal in only 2 of 16 patients, and after incubation of PRP with ASA 1 of these 2 remained normal.

The corrective effect of dilutions of platelet poor plasma (PPP) on the ristocetin response of washed platelets (von Willebrand’s factor, vWf ) was measured in 21 normals and 12 patients with vWd. All patients with vWd had abnormal levels. There was a significant correlation between aggregation rate and vWf in patients with vWd but not in normals. Both tests appear to measure closely related defects, and the aggregation rate is as specific as the vWf level for the diagnosis of clinically affected patients.