The Merkle laboratory studies the molecular and cellular basis of human diseases using a combination of human cellular models and animal models. We have a particular interest in obesity, which leads to millions of premature deaths each year, lacks broadly effective treatments, and is associated with the aberrant function of specific neuron types in the hypothalamus. We developed methods to differentiate human pluripotent stem cells (hPSCs) into functional hypothalamic cell types in culture, enabling us to study their function in health and obesity using a range of cutting-edge techniques including genome engineering, single-cell transcriptomics, quantitative peptidomics, high content imaging, calcium imaging, and xenotransplantation. Research in my laboratory revolves around three areas:
1) Basic biology of human hypothalamic neurons
We are interested in understanding how hPSC-derived hypothalamic neurons 1) develop in vitro, 2) sense and respond to hormones (e.g. leptin), nutrients and drugs, 3) regulate their production and secretion of biologically active neuropeptides, and 4) resemble their counterparts in the mouse and human brain. These efforts provide basic biological insights and provide a baseline to which neurons carrying obesity-associated mutations or exposed to obesity-associated environmental factors can be compared. We have found by single-cell RNA sequencing that our methods generate a broad array of behaviourally and physiologically relevant neuropeptidergic hypothalamic cell types. We developed methods to quantify peptides derived from proopiomelanocortin (POMC) and demonstrated that cultured human neurons process POMC much in the same way as was seen in primary human brain samples. We have shown that human hypothalamic neurons respond to leptin, and are dissecting the molecular pathways by which leptin signalling alters gene expression and function.
2) Genetic and environmental contributions to obesity
The study of rare and highly penetrant obesity-associated mutations has revealed the importance of the leptin/melanocortin system, but the mechanisms by which most obesity-associated mutations act are still poorly understood. We are using CRISPR/Cas9 to introduce mutations observed in human patients into hPSCs, that are then differentiated into hypothalamic neurons and phenotypically compared to their isogenic controls. We are also exposing hypothalamic neurons to obesity-associated environmental factors to test whether they might contribute to obesity by acting on the hypothalamus, either directly on neurons or indirectly via other cell types.
3) Translation and in vivo models
We hypothesize that given the central role that the leptin/melanocortin system plays in the regulation of energy homeostasis, that drugs potentiating leptin signalling or the processing and secretion of POMC-derived peptides have therapeutic potential to treat obesity. We are therefore seeking to identify compounds that have this effect in vitro, and plan to test their efficacy in vivo. In addition, we have previously demonstrated that human hypothalamic neurons survive transplantation into the mouse brain, and are planning to extend these studies to test the functional effects that transplanted human cells have on feeding behaviour and body weight in the context of obesity.
Outstanding graduate and postdoctoral candidates interested in joining our team are encouraged to write me directly.
Kirwan P, Kay R, Brouwers B, Herranz-Perez V, Jura M, Larraufie P, Bartels B, Pembroke J, White A, Gribble F, Reimann F, Farooqi IS, O’Rahilly S, and Merkle FT§. Human POMC processing in vitro and in vivo revealed by quantitative peptidomics. Pre-print. BioRxiv, 31 Jan 2018. DOI:10.1101/257121.
Merkle FT*, Ghosh S*, Kamataki N, Mitchell J, Avior Y, Mello C, Kashin S, Mekhoubad S, Ilic D, Charlton M, Saphier G, Handsaker RE, Genovese G, Bar S, Benvenisty N, McCarroll S, Eggan K. Human pluripotent stem cells recurrently acquire and expand dominant negative P53 mutations. Nature, E-pub. 26 April 2017. DOI 10.1038/nature22312. PMID: 28445466 PMC5427175. IF: 38.1
Merkle FT*, Neuhausser WM*, Santos D, Valen E, Gagnon JA, Maas K, Sandoe J, Schier AF, Eggan K. Efficient CRISPR-Cas9-mediated generation of knockin human pluripotent stem cells lacking undesired mutations at the targeted locus. Cell Rep. 2015 May 12;11(6):875-83. doi: 10.1016/j.celrep.2015.04.007. PMID: 25937281.PMCID:PMC5533178
Merkle FT, Maroof A, Wataya T, Sasai Y, Studer L, Eggan K, Schier AF. Generation of neuropeptidergic hypothalamic neurons from human pluripotent stem cells. Development. 2015 Feb 15;142(4):633-43. doi: 10.1242/dev.117978. PMID:25670790. PMCID:PMC4325380
Merkle FT, Eggan K. Modeling human disease with pluripotent stem cells: from genome association to function. Cell Stem Cell. 2013 Jun 6;12(6):656-68. doi: 10.1016/j.stem.2013.05.016. PMID:23746975.
Merkle FT, Mirzadeh Z, Alvarez-Buylla A. Mosaic organization of neural stem cells in the adult brain. Science. 2007 Jul 20;317(5836):381-4. PMID:17615304.
Additional publications are available at: http://www.ncbi.nlm.nih.gov/pubmed/?term=merkle+ft