During human evolution, the knee adapted to the biomechanical demands of bipedalism by altering chondrocyte developmental programs. This adaptive process was likely not without deleterious consequences to health. Today, osteoarthritis occurs in 250 million people, with risk variants enriched in non-coding sequences near chondrocyte genes, loci that likely became optimized during knee evolution. We explore this relationship by epigenetically profiling joint chondrocytes, revealing ancient selection and recent constraint and drift on knee regulatory elements, which also overlap osteoarthritis variants that contribute to disease heritability by tending to modify constrained functional sequence. We propose a model whereby genetic violations to regulatory constraint, tolerated during knee development, lead to adult pathology. In support, we discover a causal enhancer variant (rs6060369) present in billions of people at a risk locus (GDF5-UQCC1), showing how it impacts mouse knee-shape and osteoarthritis. Overall, our methods link an evolutionarily novel aspect of human anatomy to its pathogenesis.

XLαs, a variant of the stimulatory G protein α-subunit (Gsα), can mediate receptor-activated cAMP generation and, thus, mimic the actions of Gsα in transfected cells. However, it remains unknown whether XLαs can act in a similar manner in vivo. We have now generated mice with ectopic transgenic expression of rat XLαs in the renal proximal tubule (rptXLαs mice), where Gsα mediates most actions of PTH. Western blots and quantitative RT-PCR showed that, while Gsα and type-1 PTH receptor levels were unaltered, protein kinase A activity and 25-hydroxyvitamin D 1-α-hydroxylase (Cyp27b1) mRNA levels were significantly higher in renal proximal tubules of rptXLαs mice than wild-type littermates. Immunohistochemical analysis of kidney sections showed that the sodium-phosphate cotransporter type 2a was modestly reduced in brush border membranes of male rptXLαs mice compared to gender-matched controls. Serum calcium, phosphorus, and 1,25 dihydroxyvitamin D were within the normal range, but serum PTH was ∼30% lower in rptXLαs mice than in controls (152 ± 16 vs. 222 ± 41 pg/ml; P < 0.05). After crossing the rptXLαs mice to mice with ablation of maternal Gnas exon 1 (E1(m-/+)), male offspring carrying both the XLαs transgene and maternal Gnas exon 1 ablation (rptXLαs/E1(m-/+)) were significantly less hypocalcemic than gender-matched E1(m-/+) littermates. Both E1(m-/+) and rptXLαs/E1(m-/+) offspring had higher serum PTH than wild-type littermates, but the degree of secondary hyperparathyroidism tended to be lower in rptXLαs/E1(m-/+) mice. Hence, transgenic XLαs expression in the proximal tubule enhanced Gsα-mediated responses, indicating that XLαs can mimic Gsα in vivo.

Aberrant activation of the Wnt/β-catenin signaling pathway is a critical event in advanced prostate cancer, but the genetic alterations which activate the Wnt signaling pathway in many other cancers are rarely observed in prostate cancer. Other molecular mechanisms that regulate the Wnt signaling pathway in prostate cancer remain to be identified. Here it is demonstrated that KIF3a, a subunit of kinesin-II motor protein, functions as an agonist of the Wnt signaling pathway in prostate cancer. KIF3a is up-regulated in the majority of human prostate cancer cell lines and primary tumor biopsies. The expression levels of KIF3a correlate with a higher Gleason score, TNM grade, and metastatic status of prostate cancer. Moreover, exogenous expression of KIF3a promoted cell growth in the benign prostate cells, whereas silencing KIF3a in cancer cells decreased cell proliferation, anchorage-independent cell growth, and cell migration/invasion. Mechanistically, KIF3a increases CK1-dependent DVL2 phosphorylation and β-catenin activation in prostate cancer cells, leading to transactivation of the Wnt signaling target genes such as Cyclin D1, HEF1, and MMP9. These findings support the notion that up-regulation of KIF3a is causal of aberrant activation of Wnt signaling in advanced prostate cancer through the KIF3a-DVL2-β-catenin axis. Implications Inactivation of KIF3a may improve survival of patients with advanced prostate cancer in which Wnt signaling is activated.

IκB kinase β (IKKβ), a central coordinator of inflammatory responses through activation of nuclear factor-κB (NF-κB), has been implicated as a critical molecular link between inflammation and metabolic disorders; however, the role of adipocyte IKKβ in obesity and related metabolic disorders remains elusive. Here we report an essential role of IKKβ in the regulation of adipose remodeling and adipocyte survival in diet-induced obesity. Targeted deletion of IKKβ in adipocytes does not affect body weight, food intake, and energy expenditure but results in an exaggerated diabetic phenotype when challenged with a high-fat diet (HFD). IKKβ-deficient mice have multiple histopathologies in visceral adipose tissue, including increased adipocyte death, amplified macrophage infiltration, and defective adaptive adipose remodeling. Deficiency of IKKβ also leads to increased adipose lipolysis, elevated plasma free fatty acid (FFA) levels, and impaired insulin signaling. Mechanistic studies demonstrated that IKKβ is a key adipocyte survival factor and that IKKβ protects murine and human adipocytes from HFD- or FFA-elicited cell death through NF-κB–dependent upregulation of antiapoptotic proteins and NF-κB–independent inactivation of proapoptotic BAD protein. Our findings establish IKKβ as critical for adipocyte survival and adaptive adipose remodeling in obesity.

GWAS have identified hundreds of height-associated loci. However, determining causal mechanisms is challenging, especially since height-relevant tissues (e.g. growth plates) are difficult to study. To uncover mechanisms by which height GWAS variants function, we performed epigenetic profiling of murine femoral growth plates. The profiled open chromatin regions recapitulate known chondrocyte and skeletal biology, are enriched at height GWAS loci, particularly near differentially expressed growth plate genes, and enriched for binding motifs of transcription factors with roles in chondrocyte biology. At specific loci, our analyses identified compelling mechanisms for GWAS variants. For example, at CHSY1, we identified a candidate causal variant (rs9920291) overlapping an open chromatin region. Reporter assays demonstrated that rs9920291 shows allelic regulatory activity, and CRISPR/Cas9 targeting of human chondrocytes demonstrates that the region regulates CHSY1 expression. Thus, integrating biologically relevant epigenetic information (here, from growth plates) with genetic association results can identify biological mechanisms important for human growth.