Pharmacological therapies for monogenic obesity caused by MC4R dysfunction

PhDMutations in the melanocortin-4 receptor (MC4R) are the most common cause of monogenic obesity. The majority of MC4R mutations are predicted to cause the receptor to aberrantly fold. Misfolded MC4R fails to traffic to the plasma membrane (PM) and is retained in the endoplasmic reticulum (ER). Recent studies with other G-protein coupled receptors have shown that stabilisation of misfolded receptor, by pharmacological chaperones, promotes trafficking to the cell surface where the receptor may be functional. The objective of this thesis was to develop a rapid throughput cell culture based assay to monitor MC4R trafficking to the PM and to screen chemical chaperones and inducers and inhibitors of endogenous molecular chaperones, for the ability to promote folding and cell surface expression of mutant MC4R. The work presented here confirmed that clinically occurring MC4R mutants S58C, N62S, P78L, D90N, L106P, C271Y and P299H are intracellularly retained in HEK 293 cells. The cell culture assay was used to screen a number of compounds, which have been previously reported to act as chemical chaperones by stabilising protein folding. Treatment with 4-phenyl butyric acid (4-PBA) and trehalose increased total cellular levels of wild-type and mutant MC4R. The benzoquinone ansamycin, geldanamycin, has been identified as a potent inhibitor of Hsp90 activity and an inducer of the heat shock response. Geldanamycin treatment altered the cell surface expression of wild-type and mutant MC4R. Furthermore, over expression of Hsp90 co-chaperone Aha1, also effected MC4R processing. Over-expression of Hsp70 has been shown to promote the trafficking of other aberrantly folded proteins. Over-expression of Hsc70 increased trafficking levels of wild-type and mutant MC4R and promoted mutant MC4R functional expression. In conclusion this data suggests using compounds that stabilise protein folding and/or targeting endogenous molecular chaperone machineries may have efficacy for altering cell surface expression of mutant MC4R

Phase 1 clinical study of an embryonic stem cell-derived retinal pigment epithelium patch in age-related macular degeneration

Age-related macular degeneration (AMD) remains a major cause of blindness, with dysfunction and loss of retinal pigment epithelium (RPE) central to disease progression. We engineered an RPE patch comprising a fully differentiated, human embryonic stem cell (hESC)-derived RPE monolayer on a coated, synthetic basement membrane. We delivered the patch, using a purpose-designed microsurgical tool, into the subretinal space of one eye in each of two patients with severe exudative AMD. Primary endpoints were incidence and severity of adverse events and proportion of subjects with improved best-corrected visual acuity of 15 letters or more. We report successful delivery and survival of the RPE patch by biomicroscopy and optical coherence tomography, and a visual acuity gain of 29 and 21 letters in the two patients, respectively, over 12 months. Only local immunosuppression was used long-term. We also present the preclinical surgical, cell safety and tumorigenicity studies leading to trial approval. This work supports the feasibility and safety of hESC-RPE patch transplantation as a regenerative strategy for AMD

Common STAT3 variants are not associated with obesity or insulin resistance in female twins

JAMSHIDI, YALDA, THEODOSIOS KYRIAKOU, SAKINA B. GOOLJAR, LAURA J. COLLINS, CARL A. LANE, HAROLD SNIEDER, XIAOLING WANG, TIM D. SPECTOR, AND SANDRA D. O'DELL. Common STAT3 variants are not associated with obesity or insulin resistance in female twins. Obesity. 2007; 15:1634-1639. In animal models, STAT3 action in the hypothalamus and liver appears essential for normal body weight and glucose homeostasis in response to insulin. We hypothesized that variation in the STAT3 gene may be associated with body fat and/or insulin resistance in the general population. Five tagging SNPs spanning the STAT3 gene, rs8074524, rs2293152, rs2306580, rs6503695, and rs7211777 were genotyped in 2776 white female twins (mean age, 47.4 +/- 12.5 yrs) from the St Thomas' United Kingdom Adult Twin Registry (Twins UK). Minor allele frequencies were as follows: rs8074524 (0.19), rs2293152 (0.37), rs2306580 (0.06), rs6503695 (0.35), and rs7211777 (0.34). The minor allele of rs2293152 was associated with higher homeostasis model assessment index of insulin resistance (p = 0.013) in the full cohort and confirmed in sib-transmission/disequilibrium test (TDT): (p = 0.015; n = 60). However, there were no associations with fasting serum insulin or glucose or with obesity variables. Although defective STAT3 action results in obesity and insulin resistance in animal models, we failed to establish any indicative associations with common SNPs in this human study