Abnormal separation of the respiratory system from the foregut leads to the common birth defect esophageal atresia/tracheoesophageal fistula (EA/TEF) which affects 1/2,500-3000 newborns. Although the anomalycanbecorrectedwithsurgicalintervention,upto72%ofsurvivingadolescentsandadultscontinueto sufferfromrespiratoryproblemsthroughouttheirlifetime,suggestingaconnectionbetweenEA/TEFandlung abnormalities. Consistently, EA/TEF is always accompanied by abnormal lungs (e.g. lobe fusion) in animal models,althoughtheunderlyingmechanismisunknown.Werecentlyshowedthatanepithelialsaddleformed atthelung-esophagealboundarymovesupwardtosplitthelungandtracheafromtheesophagus.However, severalimportantquestionsremaintobeanswered.Howisthelunginvolvedinsaddleformationandmovement? Whatistheunderlyingcellularandmolecularmechanism?Weaimtouseacombinationoforganculture,frog, and mouse models to address these issues. Our lineage tracing data show that derivatives of respiratory progenitorcells(Nkx2.1positive)integrateintotheesophagusduringseparation.Moreover,ourpreliminarydata suggest that a unique lung epithelial progenitor subpopulation (Sox2;?Sox9;?Isl1 positive) located at the lung- esophageal boundary plays critical roles in the formation of the saddle. We further found that the loss of the transcription factor Sox2 or Isl1 in the lung progenitors, including the subpopulation, leads to EA/TEF and abnormal lungs in both frogs and mice. Interestingly, these abnormalities are accompanied by a reduction of extracellularmatrix(ECM)proteinsincludingFrasfamilymembersFras1andFrem2whichareknowntoregulate lung development. We therefore hypothesize that the Sox2/Isl1 axis regulates ECM proteins in a lung epithelialprogenitorsubpopulation(Sox2;?Sox9;?Isl1positive)thatisrequiredforrespiratory-esophageal separationandlungdevelopment.Wewilltestthehypothesiswiththreespecificaims:
Aim1 todeterminethe contributionofthelungepithelialprogenitorsubpopulationtothesaddleformationandrespiratory-esophageal separation;?Aim2totestthehypothesisthatSox2regulatesIsl1inthelungepithelialprogenitorsubpopulation to control respiratory-esophageal separation;? Aim3 to test the hypothesis that Isl1 regulates the separation process and lung development through ECM proteins. Notably, chromosomal deletion of the region covering ISL1 (and other genes) has been found in patients with EA/TEF. Our findings therefore will provide direct evidence and mechanistic insight into the role of Sox2/Isl1/ECM axis in the pathogenesis of this defect and associatedlungabnormalities.

Public Health Relevance

Abnormalseparationofthelungandtracheafromtheforegutleadstomultipleforegutmalformations includingthecommonbirthdefecttracheoesophagealfistulawhichaffects1/2000-1/3500newborns.Thisbirth defect compromises lung function at all ages. Although multiple genes have been associated with the formation of the defect, there is a gap in the understanding of the underlying cellular and molecular mechanisms.Here,weuseacombinationoforganculture,frogandmousemodelstoaddresstheissue.The proposalwillprovidenovelinsightintofundamentalmechanismswithbroadscientificandclinicalimplications.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL132996-02
Application #
9438562
Study Section
Lung Injury, Repair, and Remodeling Study Section (LIRR)
Program Officer
Lin, Sara
Project Start
2017-03-01
Project End
2021-02-28
Budget Start
2018-03-01
Budget End
2019-02-28
Support Year
2
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Columbia University (N.Y.)
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
621889815
City
New York
State
NY
Country
United States
Zip Code
10032
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