Role of SPOCK2 in susceptibility of premature infants to bronchopulmonary dysplasia – BPDSPOCK2

Bronchopulmonary dysplasia (BPD) is the most common respiratory sequelae of prematurity, and is a source of significant respiratory morbidity. It corresponds to an arrested alveolar development. Understanding of the mechanisms of this disease has evolved considerably in recent years, with the emergence of consistent arguments in favor of a strong contribution of genetic factors to this pathology. BPD can no longer be considered as only triggered by the many environmental stresses experienced by the lungs of premature babies, but as the result of gene-environment interactions.
The team of the coordinator was the first to identify a major susceptibility gene (SPOCK2), whose association to the development of BPD was common to different ethnic groups, and replicated in independent populations (GENBPD project, ANR 2009). The role of SPOCK2 in the alveolar development is currently unknown, but the team has already acquired results suggesting a significant role of this protein during this period of development. The current project aims to better understand the role of SPOCK2 in the control of normal alveolar development and/or its alterations. It also aims to identify the presence of exonic mutations in the most severe forms of BPD, not explained by environmental injuries. These goals will be achieved through the following actions:
i) generation of transgenic mouse lines allowing conditional invalidation or conditional overexpression of SPOCK2 in the lung. These models will be produced by the platform of homologous recombination of the Cochin Institute, partner of the project. They will be evaluated at baseline and after neonatal exposure to hyperoxia, which reproduces lung lesions superimposable to those of BPD. The impact of changes in lung SPOCK2 expression on alveolar development will be assessed by techniques fully mastered by the team of the coordinator: lung morphometry; mRNA and protein evaluation of the main factors known to control alveolar development, both in the bronchoalveolar lavage fluid and lung tissue.
ii) in vitro study of functional consequences on SPOCK2 expression of a polymorphism associated with BPD, which is located in the 3’untranslated region of the gene, and may potentially alter the binding site of three micro-RNAs. The vectors for this study are under construction. This study is complementary to i), because it will allow linking the susceptibility to BPD in humans to changes in SPOCK2 expression, by extrapolation from observed alterations in mice induced by comparable changes in SPOCK2 expression.
iii) exome sequencing of 10 patients selected for the extreme severity of their respiratory phenotype. The responsibility for genetic factors must be assumed to be very strong or even exclusive in these rare forms that are not explained by repeated environmental stresses. This study will identify potential mutations in SPOCK2, due to the good coverage of this gene in exome sequencing, but also on other genes.
The feasibility of this project is evidenced by the expertise of the coordinator in lung development and BPD, and the association of a high-level platform for the production of transgenic lines. The support of technical platforms, such as Integragen and the Imagine Foundation/ParisDescartes bioinformatic platform strengthens the credibility of the subject. The theme is very original, in a competitive field, and is potentially a source of innovative developments, in terms of new ways of diagnosis or treatment.