X-linked retinitis pigmentosa (XLRP) results from mutations in at least two different loci, designated RP2 and RP3, located at Xp11.3 and Xp21.1, respectively. The RP3 gene was recently isolated by positional cloning, whereas the RP2 locus was mapped genetically to a 5-cM interval. We have screened this region for genomic rearrangements by the YAC representation hybridization (YRH) technique and detected a LINE1 (L1) insertion in one XLRP patient. The L1 retrotransposition occurred in an intron of a novel gene that consisted of five exons and encoded a polypeptide of 350 amino acids. Subsequently, nonsense, missense and frameshift mutations, as well as two small deletions, were identified in six additional patients. The predicted gene product shows homology with human cofactor C, a protein involved in the ultimate step of beta-tubulin folding. Our data provide evidence that mutations in this gene, designated RP2, are responsible for progressive retinal degeneration.

Functional L1 elements are autonomous retrotransposons that can insert into human genes and cause disease. To date, 10 of 12 known L1 retrotranspositions into human genes have been found to be 5"-truncated and incapable of further retrotransposition. Here we report the nucleotide sequences of the two full-length L1 elements, L1beta-thal and L1RP, that have inserted into the beta-globin and retinitis pigmentosa-2 (RP2) genes, respectively. L1beta-thal is 99. 4% identical to a consensus sequence of active human L1s, while L1RP is 99.9% identical. Both elements retain impressive capacity for high frequency retrotransposition in cultured HeLa cells. Indeed, L1RP is the most active L1 isolated to date. Our data indicate that not all L1 insertions into human genes are 'dead on arrival'. Our findings also lend further credence to the concept of cis preference, that the proteins encoded by a particular L1 preferentially act upon their encoding RNA as opposed to other L1 RNAs.

Brown adipose tissue has gained interest as a potential target to treat obesity and metabolic diseases. Irisin is a newly identified hormone secreted from skeletal muscle enhancing browning of white fat cells, which improves systemic metabolism by increasing energy expenditure in mice. The discovery of irisin raised expectations of its therapeutic potential to treat metabolic diseases. However, the effect of irisin in humans is unclear. Analyses of genomic DNA, mRNA and expressed sequence tags revealed that FNDC5, the gene encoding the precursor of irisin, is present in rodents and most primates, but shows in humans a mutation in the conserved start codon ATG to ATA. HEK293 cells transfected with a human FNDC5 construct with ATA as start codon resulted in only 1% full-length protein compared to human FNDC5 with ATG. Additionally, in vitro contraction of primary human myotubes by electrical pulse stimulation induced a significant increase in PGC1α mRNA expression. However, FNDC5 mRNA level was not altered. FNDC5 mRNA expression in muscle biopsies from two different human exercise studies was not changed by endurance or strength training. Preadipocytes isolated from human subcutaneous adipose tissue exhibited differentiation to brite human adipocytes when incubated with bone morphogenetic protein (BMP) 7, but neither recombinant FNDC5 nor irisin were effective. In conclusion, our findings suggest that it is rather unlikely that the beneficial effect of irisin observed in mice can be translated to humans.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is a potential novel strategy for treatment of CVD. Alirocumab is a fully human PCSK9 monoclonal antibody in phase 3 clinical development. We evaluated the antiatherogenic potential of alirocumab in APOE*3Leiden.CETP mice. Mice received a Western-type diet and were treated with alirocumab (3 or 10 mg/kg, weekly subcutaneous dosing) alone and in combination with atorvastatin (3.6 mg/kg/d) for 18 weeks. Alirocumab alone dose-dependently decreased total cholesterol (−37%; −46%, P < 0.001) and TGs (−36%; −39%, P < 0.001) and further decreased cholesterol in combination with atorvastatin (−48%; −58%, P < 0.001). Alirocumab increased hepatic LDL receptor protein levels but did not affect hepatic cholesterol and TG content. Fecal output of bile acids and neutral sterols was not changed. Alirocumab dose-dependently decreased atherosclerotic lesion size (−71%; −88%, P < 0.001) and severity and enhanced these effects when added to atorvastatin (−89%; −98%, P < 0.001). Alirocumab reduced monocyte recruitment and improved the lesion composition by increasing the smooth muscle cell and collagen content and decreasing the macrophage and necrotic core content. Alirocumab dose-dependently decreases plasma lipids and, as a result, atherosclerosis development, and it enhances the beneficial effects of atorvastatin in APOE*3Leiden.CETP mice. In addition, alirocumab improves plaque morphology.

While white adipose tissue (AT) is an energy storage depot, brown AT is specialized in energy dissipation. Uncoupling protein 1 (UCP1)-expressing adipocytes with a different origin than classical brown adipocytes have been found in white AT. These "brite" (brown-in-white) adipocytes may represent a therapeutic target to counteract obesity. Bone morphogenetic proteins (BMPs) play a role in the regulation of adipogenesis. Based on studies with murine cells, BMP4 is assumed to induce stem cell commitment to the white adipocyte lineage, whereas BMP7 promotes brown adipogenesis. There is evidence for discrepancies between mouse and human AT. Therefore, we compared the effect of BMP4 and BMP7 on white-to-brown transition in primary human adipose stem cells (hASCs) from subcutaneous AT. Long-term exposure of hASCs to recombinant BMP4 or BMP7 during differentiation increased adipogenesis, as determined by lipid accumulation and peroxisome proliferator-activated receptor-␥ (PPAR␥) expression. Not only BMP7, but also BMP4, increased UCP1 expression in hASCs and decreased expression of the white-specific marker TCF21. The ability of hASCs to induce UCP1 in response to BMP4 and BMP7 markedly differed between donors and could be related to the expression of the brite marker CD137. However, mitochondrial content and oxygen consumption were not increased in hASCs challenged with BMP4 and BMP7. In conclusion, we showed for the first time that BMP4 has similar effects on white-to-brown transition as BMP7 in our human cell model. Thus the roles of BMP4 and BMP7 in adipogenesis cannot always be extrapolated from murine to human cell models. bone morphogenetic proteins; primary human preadipocytes; adipogenesis; brite adipocytes ADIPOSE TISSUE (AT) PLAYS a crucial role in the regulation of energy homeostasis. Functionally, AT can be subdivided into white AT and brown AT. While white AT is the main site of energy storage and provides substrates in terms of energy needs by releasing free fatty acids and glycerol, brown AT metabolizes triglycerides to generate heat in adaptation to a cold environment (32). This unique function of brown AT is due to a high mitochondrial density and to the presence of uncoupling protein 1 (UCP1). Until recently, brown AT was believed to play a negligible role in the adult human. However, it gained substantial interest since active brown AT has been shown to be present in adults by five independent groups (4, 23, 38, 40, 43) and brown AT activity was negatively associated with increasing body mass index (BMI) (23, 38, 43). Furthermore, UCP1-expressing brown-like adipocytes have been discovered within white AT after cold exposure (31). These so called "brite" (brown-in-white) adipocytes arise from white preadipocytes (19), whereas classical brown adipocytes are derived from the myogenic lineage (29,35). Both increasing brown AT activity and promoting the induction of brite adipocytes in white AT represent strategies to counteract obesity. Pharmacological agents, like peroxisome proliferatoractivated recep...