In cultured cells, the adaptor protein SH3PXD2B is capable of recruiting a variety of proteins involved in invadosome assembly and function. It is therefore considered as an essential organizer of invadosomes active in cellular responses that require extracellular matrix degradation. Despite increasing knowledge about its properties and functions at the molecular and cellular levels, its physiological role in whole animals has not previously been assessed. Here, we present that SH3PXD2B is essential for normal postnatal development and disrupting SH3PXD2B can lead to glaucoma.
Our work on SH3PXD2B is based on nee, a spontaneous mutation in mice which arose on an inbred background. Mice homozygous for the nee mutation were initially noted to exhibit runted growth, craniofacial abnormalities and ocular defects. Our additional physiological characterization has uncovered skeletal abnormalities, hearing impairment, infertility and a form of lipodystrophy. Using genetic mapping and DNA sequencing, the cause of nee phenotypes was identified as a 1-bp deletion within the Sh3pxd2b gene on mouse Chromosome 11. The nee mutation is predicted to cause a frameshift and a protein truncation altering a portion of the third SH3 domain and deleting the entire fourth SH3 domain. Molecular analysis showed that the fourth SH3 domain of SH3PXD2B can interact with a transmembrane member of a disintegrin and metalloproteinase family of proteins, ADAM15, and that GFP tagged SH3PXD2B protein truncation mislocalizes to the nucleus. Therefore, the mutant allele likely disrupts the normal function of SH3PXD2B and leads to nee phenotypes.
The initial ocular abnormalities of nee mutants suggested that they may develop glaucoma. To test this hypothesis, we performed detailed clinical and histological analyses. We find that nee mutants exhibit elevated intraocular pressure likely caused by a severe iridocorneal adhesion present early in development. During the same time that intraocular pressure becomes elevated, retinal ganglion cells are damaged and optic nerve degeneration ensues. These results demonstrate that nee mutants develop an early onset form of closed angle glaucoma. To test the potential involvement of SH3PXD2B in human diseases, DNA sequencing analysis has been initiated in patients with developmental, primary open angle and syndromic glaucoma, and several missense variations have been identified. In conclusion, my results demonstrate a critical role of SH3PXD2B in normal development of multiple tissues and suggest that mutations in SH3PXD2B may also contribute to glaucoma.