Arya Mani, MD, FACC, FAHA

1. Hyperlipidemia and fatty liver disease

Wnt coreceptor LDL receptor-related protein 6 (LRP6) gene was the very first monogenic cause of coronary artery disease (OMIM: ADCAD2) and MetS (Science 2007), which we discovered in our lab. Genotype phenotype correlation showed that the mutations impact a number of metabolic phenotypes, including hypercholesterolemia and nonalcoholic fatty liver disease (NAFLD). This discovery caused a paradigm shift by establishing a causal link between impaired LRP6 /Wnt signaling and CAD and its associated metabolic traits. Having unique access to the study populations, we investigated the role of LRP6 in regulation of cholesterol uptake in primary human cells and tissues and demonstrated its role in clathrin-mediated LDLR endocytosis. Mice generated in our lab with the human LRP6 mutation (LRP6^R611C) exhibited elevated plasma LDL and TG levels and developed steatohepatitis and steatofibrosis. The molecular dissection of the disease pathways showed that the LRP6 mutation triggers hepatic de-novo lipogenesis (DNL) via TCF7L2-dependent activation of mTOR nutrient sensing pathway. These traits were rescued by in vivo administration of rmWnt3a, identifying Wnt pathways as an attractive therapeutic target against NASH. The investigation of a large, inbred population with extremely high prevalence obesity, MetS and NAFLD led to the discovery of founder mutations in DYRK1B gene as the second monogenic cause of MetS and NAFLD. Further studies revealed that DYRK1B protein levels are increased in the liver of most patients with NASH and in mice fed with a high calorie diet. Strikingly, the induction of hepatic Dyrk1b in mice on chow diet enhanced de novo lipogenesis (DNL), fatty-acid uptake, and TAG secretion and caused NASH and hyperlipidemia by activating mTORC2 pathway. Conversely, knockdown of Dyrk1b was protective against these traits. These findings identify DYRK1B as an attractive target for NAFLD, motivating further investigations into the utility of Dyrk1a/b proteins as attractive drug targets for NAFLD.

• Neha Bhat, Anand Narayanan, Mohsen Fathzadeh, Mario Kahn, Leigh Goedeke, Noemi Vila, Arpita Neogi, Henry N Ginsberg, Dhanpat Jain, Carlos Fernandez-Hernando, Gerald I Shulman, Arya Mani. ­Dyrk1b is a novel therapeutic target for nonalcoholic steatohepatitis (NASH) and insulin resistance J Clin Invest. 2021Dec 2:e153724. PMID: 34855620
• Wang S, Song K, Srivastava R, Dong C, Go GW, Li N1, Iwakiri Y, Mani A. Nonalcoholic fatty liver disease induced by noncanonical Wnt and its rescue by Wnt3a. FASEB 2015 PMID: 25917329
• Go GW, Srivastava R, Hernandez-Ono A, Gang G, Smith SB, Carmen J, Booth CJ, Ginsberg HN, and Mani A. The Combined Hyperlipidemia Caused by Impaired Wnt-LRP6 signaling is reversed by Wnt3a Rescue. Cell Metab. 2014;19(2):209-220. PMID: 24506864
• Liu W, Mani S, Davis NR, Sarrafzadegan N, Kavathas PB, Mani A. Mutation In EGFP Domain of LDL Receptor-Related Protein 6 Impairs Cellular LDL Clearance. Circulation Research 2008;103(11):1280-1288. PMID:18948618

2. Atherosclerosis Our lab was the first to discover the role of altered Wnt signaling in atherosclerosis. In collaboration with a team of cardiothoracic surgeons at Yale we showed the dramatic increase in expression of Wnt coreceptor LRP6 in human atherosclerotic coronary arteries as a response to injury. By dissecting the molecular pathways in human VSMCs, we were able to show that LRP6 forms a complex with PDGFR-β, enhances its lysosomal degradation, increases VSMC differentiation and prevents excessive proliferation. These functions were severely impaired by LRP6 mutations resulting in the activation of noncanonical Wnt signaling. Our findings implicated LRP6 as a critical modulator of PDGF-dependent regulation of cell cycle in VSMC and showed that loss of this function contributes to development of early onset atherosclerosis. One of the most exciting developments in our lab was the generation of a novel coronary artery disease mouse model. Mice carrying the human LRP6^R611C mutation displayed dramatic obstructive CAD on high fat diet and exhibited an accelerated atherosclerotic burden on LDLR knockout background. The dissection of disease pathways revealed that impaired LRP6 activity triggers non-canonical Wnt signaling, culminating in diminished TCF7L2 and increased activation of PDGF signaling. Strikingly, Wnt3a administration to LRP6^R611C mice improved the activity of LRP6 and its downstream signaling pathway, led to TCF7L2-dependent VSMC differentiation, and rescued post carotid injury neointima formation. Accordingly, we showed in a separate study that mice deficient for TCF7L2 develop wire injury-induced carotid intimal hyperplasia, while the overexpression of TCF7L2 is protective against it and can rescue post-injury intimal hyperplasia of LRP6^R611C mice. These findings underscored the critical role of intact Wnt signaling in maintaining the normal structure of the vessel wall, established a causal link between impaired LRP6/TCF7L2 activities and arterial disease and identified Wnt/TCF7L2 as an attractive target for the treatment of CAD. Motivated by these remarkable findings, we are currently working with the industry to study the effect of Wnt-inhibitors antagonists to treat intimal hyperplasia.

• Keramati AR, Singh R, Lin A, Faramarzi S, Ye Z, Mane S, Tellides G, Lifton RP, and Mani A. Wild-type LRP6 inhibits, whereas atherosclerosis-linked LRP6R611C increases PDGF-dependent vascular smooth muscle cell proliferation. Proc Natl Acad Sci U S A ,2011, 108(5):1914-8, PMC3033290.
• Srivastava R, Zhang J, Go GW, Narayanan A, Nottoli TP, Mani A. Impaired LRP6-TCF7L2 activity enhances smooth muscle cell plasticity and causes coronary artery disease. Cell Reports,2015.13(4):746-59 PMID: 26489464

c. Srivastava R, Rolyan H, Xie Y, Li N, Bhat N, Hong L, Esteghamat F, Adeniran A, Geirsson A, Zhang J, Ge G, Nobrega M, Martin KA, Mani A. TCF7L (Transcription Factor 7-Like ) Regulation of GATA6 (GATA-Binding Protein 6)-Dependent and -Independent Vascular Smooth Muscle Cell Plasticity and Intimal Hyperplasia Arterioscler Thromb Vasc Biol. 2019 Feb;39(2):250-262 PMID:30567484

3. Molecular Genetics of Diabetes and Insulin Resistance The molecular mechanisms underlying insulin resistance are poorly understood. Our studies using different genetic mouse models have revealed that altered function of skeletal muscle, endothelial cells, and hepatocytes can all impair glucose tolerance. Our human genetic studies had established a causal link between missense mutations in LRP6 and DYRK1B genes and type 2 diabetes. LRP6 mutation carriers exhibited hyperinsulinemia and reduced insulin sensitivity compared to noncarrier relatives in response to oral glucose ingestion, which correlated with a significant decline in the skeletal muscle expression of the insulin receptor and canonical insulin signaling activity. Further investigations showed that the LRP6(R611C) mutation diminishes TCF7L2-dependent transcription of the IR while it triggers mTORC1-dependent IRS1/2-phosphorylation and inactivation. We have recently shown Dyrk1b gain of function causes insulin resistance by increasing plasma membrane sn-1,2-diacylglyerol levels and PKCε-mediated IRKT¹¹⁵⁰ phosphorylation in the liver, which results in impaired activation of hepatic insulin signaling and reduced hepatic glycogen storage. In a separate study we showed that the loss of Apelin in the endothelial cell increases fatty acid uptake and causes insulin resistance.

• Liu W, Singh R, Choi CS, Lee HY, Keramati AR, Samuel VT, Lifton RP, Shulman GI, Mani A. Low density lipoprotein (ldl) receptor-related protein 6 (lrp6) regulates body fat and glucose homeostasis by modulating nutrient sensing pathways and mitochondrial energy expenditure. J Biol Chem. 2012;287:7213-7223PMC3293520
• (featured article) Singh R, De Aguiar RB, Naik S, Mani S, Ostadsharif K, Wencker D, Sotoudeh M, Malekzadeh R, Sherwin RS, Mani A. Lrp6 enhances glucose metabolism by promoting tcf7l2-dependent insulin receptor expression and igf receptor stabilization in humans. Cell Metab. 2013;17:197-209PMC3589523
• Cheol Hwangbo, Jingxia Wu, Irinna Papangeli, Takaomi Adachi, Bikram Sharma, Saejeong Park, Lina Zhao, Hyekyung Ju, Gwang-woong Go,¹ Guoliang Cui, Mohammed I.N. Ahmed, Judith Job, Rajadas, Stephanie L. Kwei, Ming O. Li, Alan R. Morrison, Thomas Quertermous, Arya Mani, Kristy Red-Horse, Hyung J. Chun^, Endothelial APLNR regulates tissue fatty acid uptake and is essential for apelin’s glucose lowering effects Sci Transl Med. 2017 Sep 13;9. PMID:28904225
• Neha Bhat, Anand Narayanan, Mohsen Fathzadeh, Mario Kahn, Leigh Goedeke, Noemi Vila, Arpita Neogi, Henry N Ginsberg, Dhanpat Jain, Carlos Fernandez-Hernando, Gerald I Shulman, Arya Mani. ­Dyrk1b is a novel therapeutic target for nonalcoholic steatohepatitis (NASH) and insulin resistance J Clin Invest. 2021Dec 2:e153724. PMID: 34855620

4. The molecular genetics of patent ductus arteriosus My laboratory has been interested in the pathogenesis of patent ductus arteriosus as a gateway to the discovery of pathways that maintain patency of arterial lumens. We have mapped and identified disease genes for syndromic and nonsyndromic, autosomal dominant and recessive patent ductus arteriosus. The in vivo and in vitro characterization of disease genes has led to discovery of genetic networks that alter neural crest cell migration and differentiation. Specifically, we discovered that increased Wnt activation causes the patency of the ductus by impairing smooth muscle cell proliferation, a process that is sharply opposite to the pathogenesis of CAD in mice with defective Wnt coreceptor LRP6. This finding supports our earlier discoveries, implicating Wnt signaling in vascular remodeling.

• Lingjuan Hong, Na Li, Victor Gasque, Sameet Mehta, lupeng ye, yinyu wu, jinyu li, Andreas Gewies, Jürgen Ruland, Karen Hirschi, Anne Eichmann, Caroline Hendry, David van dijk, Arya Mani. Prdm6 controls heart development by regulating neural crest cell specification and migration. JCI Insight (in press)
• Li N, Subrahmanyan L, Smith E, Yu X, Zaidi,S, Choi M, Mane S, Nelson-Williams C, Bahjati M, Kazemi M, Hashemi M, Fathzadeh M, Narayanan A, Tian L, Montazeri F Mani M, Begleiter ML, Coon BG, Lynch HT, Olson EN, Zhao Ho, Ruland J, Lifton RP, and Mani A. Mutations in the histone modifier PRDM6 are associated with isolated nonsyndromic patent ductus arteriosus. Am J Hum Genet. 2016; 98(6):1082-91PMID: 27181681
• Mani A, Radhakrishnan J, Farhi A, Carew KS, Warne CA, Nelson-Williams C, Day RW, Pober B, State MW, Lifton RP. Syndromic patent ductus arteriosus: evidence for haplo insufficient TFAP2B mutations and identification of a linked sleep disorder. Proc Natl Acad Sci U S A 2005;102: 2975-2979. PMC549488
• Mani A, Meraji SM, Houshyar R, Radhakrishnan J, Mani A, Ahangar M Rezaie TM, Taghavinejad MA, Broumand B, Zhao H, C. Nelson-Williams C, Lifton R. Finding genetic contributions to sporadic disease: A recessive locus at 12q24 commonly contributes to patent ductus arteriosus. Proc Natl Acad Sci U S A 2002;99:15054-15059. PMC137543

5. Genetics of Atrial fibrillation (AF) and arrhythmias

As the director of the Cardiovascular Genetics program, I have access to a large number of outlier kindreds with rare familial cardiovascular disorders. This has provided us with a unique opportunity to discover novel genes for diseases of the heart rhythm. The strong relationship between cardiac arrhythmias and atherosclerosis and metabolic syndrome in particular drives our interest. Our investigations resulted recently in identification of the first disease gene for slow atrial fibrillation and the establishment of its link to stroke.

• Abou Ziki MD, Seidelmann SB, Smith E, Atteya G, Jiang Y, Fernandes RG, Marieb MA, Akar JG, Mani A. Deleterious protein-altering mutations in the SCN10A voltage-gated sodium channel gene are associated with prolonged QT. Clin Genet. 2018 ;93(4):741-75; PMID: 28407228
• Seidelmann SB, Smith E, Subrahmanyan L, Dykas D, Abou Ziki MD, Azari B, Hannah-Shmouni F, Jiang Y, Akar JG, Marieb M, Jacoby D, Bale AE, Lifton RP, Arya Mani. The Application of Whole Exome Sequencing in the Clinical Diagnosis and Management of Inherited Cardiovascular Diseases in Circ: Cardiovasc Genet 2017 Feb;10(1):e001573. doi: 10.116, PMID: 28087566 (editor’s Choice) Abou Ziki, M; Bhat, N; Neogi, A; abboud JM; Chouairi SF; Driscoll T; Ugwu, Nelson N; Ya, Liu; Smith E; Schwartz, M; Akar, J; Mani, A . Epistatic interaction of PDE4DIP and DES mutations in familial atrial fibrillation with slow conduction. Hum Mutat. 2021;42(10):1279-1293.PMID: 34289528Adults.