Anthony B. Firulli, PhD
Carleton Buehl McCulloch Professor of Pediatrics
In July, 2003, I began working for the Indiana School of Medicine, as an Associate Professor, in the Department of Pediatrics, at the Herman B Wells Center for Pediatric Research. In July, 2009, I was promoted to Professor in the Departments of Pediatrics, Medical and Molecular Genetics, Anatomy & Cell Biology/Biochemistry.
Beginning in January, 2014, I was awarded the title of Carleton Buehl McCulloch Professor of Pediatrics.
For well over 20 years, my independent career focus has been on gaining an understanding of the role that the bHLH Hand/Twist-family of proteins plays during heart development. My group has established that these factors have broad dimerization characteristics and that phosphoregulation of these proteins helps define bHLH partner choice. We have gone on to show that Hand/Twist-family gene dosage within a cell defines a bHLH code, which orchestrates cell specification, differentiation, and morphological patterning. This mechanism is directly involved in causing the human disease. We have recently discovered that bHLH partner choice pays a key role in the patterning of the face during embryonic development. Hand1 expression within the distal cap of the 1st pharyngeal arch is not necessary for normal craniofacial morphogenesis; however when Hand1 dimer mutant knock in alleles are activated within the endogenous Hand1 expression domain, there is a pronounced mid face clefting that results from disruption of FGF and SHH signaling and causes wide spread non-cell autonomous cell death within forming 1st pharyngeal arch.
In more recent studies, we have discovered the minimal Hand1 transcriptional enhancer necessary and sufficient for recapitulating 1st pharyngeal arch expression. Regulation of this enhancer by BMP, HAND2, and DLX5 and 6 shows that Hand1 expression defines the distal cap of the 1st pharyngeal arch and provides a powerful tool to interrogate the role this distal most portion of the forming jaw has on craniofacial patterning and morphogenesis.
I am very pleased and dedicated to participate in our student research programs, being a member of graduate thesis committees, postdoctoral and graduate advisor. My professional activities also include being invited to internal, national and international meetings to speak about my research.
Online in PubMed
Titles & Appointments
- Professor of Biochemistry & Molecular Biology
- Adjunct Professor of Medical & Molecular Genetics
- Adjunct Professor of Anatomy, Cell Biology & Physiology
- Director, Program in Cardiac Developmental Biology
- Director, University of Ulster Masters Internship Program
The biological question that holds my research interest is gaining an understanding of the transcriptional mechanisms that control the cell specification and differentiation of multi-potential cells. When I was a graduate student, the myogenic basic loop-helix (bHLH) transcription factors were identified and shown to program fibroblast cell lines such as 10T1/2 to the skeletal muscle lineage. The finding that a single family of transcription factors could define cell identity led me to look for novel transcription factors that played similar roles in the specification of tissues such as the heart. These efforts resulted in my study of the Twist class of bHLH factors Hand1, Hand2, and Twist1. Unlike the myogenic bHLH transcription factors, Twist-family bHLH factors are expressed in a wide range of tissues including heart, cardiac neural crest, lateral mesoderm, the developing sympathetic nervous system and other mesenchymal cell populations during development as well as in pathologies such as cancer. In our study of the biological properties of Twist-family proteins, we discovered that unlike the myogenic bHLH factors, these bHLH factors exhibit promiscuous dimerization characteristics such that Hand1, Hand2 and Twist1 can form homo and hetero dimers in addition to heterodimers with E-proteins. This expanded dimerization profile sets up a model whereby changes in the biological function of these factors is dependent on the various bHLH proteins expressed within a given cell and the mechanisms that dictate dimer partner choice. If in fact Twist-family biological function is regulated by dimer partner choice then an obvious question: How is dimer choice regulated? Must be asked. Our first insights into the mechanisms that control Twist-family dimerization choices came from our discovery of a phosphoregulatory circuit composed of the kinases PKC and PKA and the trimeric phosphatase, PP2A, containing the B56d regulatory subunit. These enzymes modulate the phosphorylation state of Hand and Twist proteins on 2 evolutionarily conserved residues within Helix I of the bHLH domain. Florescence Resonance Energy Transfer (FRET) and in vivo expression analysis show that phosphorylation of Hand1, Hand2 and Twist1 on these conserved residues modulates dimer partner choice, and in the case of Twist1, human mutations that hobble normal phosphoregulation result in the autosomal dominant human disease Saethre Chotzen Syndrome (SCS; OMIM 101400.) Furthermore, loss of normal Twist1 phosphorylation in SCS effects Twist1's ability to antagonize the functions of Hand2 and that by reducing the gene dosage of Hand2 one can rescue the SCS phenotypes in the Twist1 haploinsufficient mouse model validating the hypothesis that Twist-family dimer choice is critical for normal development to proceed. To pursue our research goals we employ both conditional gain-of-function and loss-of-function mouse models, standard molecular and biochemical techniques as well as transcriptional analysis using in vivo and in vitro systems. We have gone on to show that dimer regulation affects craniofacial morphogenesis, that Twist1 is a master repressor or the neuronal program and have identified the regulatory control domains of Hand1. Our future efforts will further characterize the posttranslational modifications within Twist family of proteins and to explore how phosphoregulation and partner choice drive tissue-specific development programs using gene targeted mouse models that allow for the conditional activation of mutant protein expression in the wide spectrum of mesenchymal tissues that require Twist-class bHLH factors for proper development. By using large sequence data that has revealed mutations of Hand and Twist proteins found in human patients presenting with disease, we will model these mutations in vivo and deduce their contributions to congenital defects that account for 1% of all live births.
American Chemical Society: High Achievement in Chemistry Award
American Heart Association
American Heart Association: Established Investigator
American Society for Biochemistry and Molecular Biology
Editorial Boards: Developmental Biology Journal, Journal of Biological Chemistry, AIMS Genetics, Scientific Reports
Member: NIH CDD/NHLBI
Muscular Dystrophy Association: William C. Gibson Neuromuscular Disease Research Fellowship (1993-1996)
Society for Developmental Biology
Society for Neuroscience
Society for Pediatric Research
Special Review Panels: National Science Foundation, Wellcome Trust
5th Riley Heart Center Symposium on Cardiac Development "Development and Repair of the Ventricular Wall"
The goal of the Symposium is to advance the overall field of cardiovascular development through the sharing of information and facilitation of collaborative investigations. A total of 15 national and international speakers have been invited.
Desc: Glenn W. Irwin, Jr., M.D., Research Scholar Award
Org: American Heart Association
Desc: American Heart Association, Established Investigator Award
Org: Muscular Dystrophy Association
Desc: William C. Gibson Neuromuscular Disease Research Fellowship
Org: Roger Williams University
Desc: Alpha Chi Edward L. Davis Award
Org: American Chemical Society
Desc: High Achievement in Chemistry Award
Org: Who's Who Among Students in American Universities and Colleges
Desc: Who's Who Among Students in American Universities and Colleges