Functions of TBX1 : an update

Functions of TBX1:an update Antonio Baldini & Elizabeth Illingworth Telethon Institute of Genetics and Medicine & Institute of Genetics and Biophysics Napoli, Italy

Goals of Basic Research • Molecular diagnostics • Identification of the disease genes • Fnctional studies • Develop the basis for future treatments (conventional or gene therapy)

FISH Diagnosis of del22q11 del 22

Gene A Gene B A B C D E

Del22q11.2 Cen CDCREL1 CLTCL GPIB RANBP1 DGCR6 GNB1L SLC25A1 ZNF74 PRODH HTF9C STK22A UFD1L LZTR1 NLVCF ARVCF CDC45 HIRA TRXR2 ES2EL COMT HCF2 CRKL CLD5 GSCL TBX1 IDD T10 3Mb (90%) 1.5Mb (10%)

? Genes and clinical findings in multigene deletion syndromes Deleted region Genes a c h g b d e f Clinical findings

Mouse models and human genetic diseases “Chromosome engineering” Generation of the first animal model of del22q11.2 (Lindsay-Illingworth, 1999) Df1 mouse -Interrupted aortic arch -Small Thymus -Small parathyroids -Neurobehavioral abnormalities

Identification of the critical gene in the mouse del22q11 Tbx1 Cdcrel1 Idd Es2el Comt Ufd1l Hira Df1 Lindsay-Illingworth et al., 2001 Jerome et al., 2001 Merscher et al., 2001

Mutations of TBX1found in VCFS patientswithout deletion Yagi et al., 2003 Paylor et al., 2006 Zweier et al., 2007

TBX1 mutations F157Y G319S L411P TBX1 NLS1 T-box H194Q 1250delC T-box T-box 1320-1342del

Gene Functions • Definition of developmental processes that require Tbx1. • Definition of the critical time(s) when Tbx1 should carry out its function.

+ - Tbx1 The developmental process(heart) expansion differentiation Progenitor cells Specialized, differntiated cells (e.g. cardiac muscle cells)

Tbx1 Proliferation Differentiation Cardiac Progenitors (SHF)

How does it work (I) Tbx1 Target gene

How does it work (I) Tbx1 Target gene Activation of “target genes”

How does it work (II) Tbx1 X Y

How does it work (II) Protein-protein interactions leading to functional modification of the proteins involved X Tbx1 Y

Tbx1 A Target gene (e.g. Fgf8) (e.g. Smad1) X Tbx1 B

Tbx1-M A Target gene (e.g. Fgf8) (e.g. Smad1) X Tbx1 B

Tbx1 A Target gene (e.g. Fgf8) X (e.g. Smad1) Tbx1-M B Mutation in a VCFS patient

Tbx1 ?

How to re-establis the balance (in the mouse)? • Increase Tbx1 dosage • Excess of Tbx1 is deleterious (published examples) • Increase the dosage of target genes • Many genes involved (e.g. Fgf8). • Intervene on developmental processes • Inhibit genes that enhance differentiation or that reduce proliferation. • Reduce the sensitivity of tissues to Tbx1 dosage • ?

Critical times Mouse 8 12 10 11 7 9 Gestation days Cleft palate Heart defects 20 41 28 33 16 24 Humans Psychiatric disease ?

Future goals • Exactly define the (molecular) damage from the loss of Tbx1. • If and when there are irreversible damages. • Identify mechanisms to “boost” the one remaining copy of Tbx1, or its target genes.

Funding National Institutes of Health (NIH), USA Telethon Italia European Community Italian Ministry of University and Research

Acknowledgments (Baylor and IBT/TexasA&M) Houston Gabriella Lania Gabriella Fulcoli Cinzia Caprio Luna Pane Rosa Serrentino Diego Circolo Sara Cioffi Huansheng Xu Zhen Zhang Francesca Vitelli Li Chen Hedda Leeming Tom Huynh COLLABORATORS Elizabeth Lindsay-Illingworth Peter J Scambler Robert Schwartz

Functions of TBX1 : an update