PPIP5K2 and PCSK1 are Candidate Genetic Contributors to Familial Keratoconus

Abstract

Keratoconus (KC) is the most common corneal ectatic disorder affecting >300,000 people in the US. KC normally has its onset in adolescence, progressively worsening through the third to fourth decades of life. KC patients report significant impaired vision-related quality of life. Genetic factors play an important role in KC pathogenesis. To identify novel genes in familial KC patients, we performed whole exome and genome sequencing in a four-generation family. We identified potential variants in the PPIP5K2 and PCSK1 genes. Using in vitro cellular model and in vivo gene-trap mouse model, we found critical evidence to support the role of PPIP5K2 in normal corneal function and KC pathogenesis. The gene-trap mouse showed irregular corneal surfaces and pathological corneal thinning resembling KC. For the first time, we have integrated corneal tomography and pachymetry mapping into characterization of mouse corneal phenotypes which could be widely implemented in basic and translational research for KC diagnosis and therapy in the future.

Inositol Pyrophosphates: Signaling Molecules with Pleiotropic Actions in Mammals

“…Keratoconus is a disorder of the eye in which progressive thinning of the cornea and its outward conical protrusion occur, resulting in blurry vision, nearsightedness, astigmatism, and light sensitivity. Recent whole-genome sequencing in familial keratoconus patients identified mutations in PPIP5K2 that were responsible for 1-IP7/IP8 synthesis [69]. PPIP5K is unique because it contains both kinase and phosphatase domains, which are the biochemical foundations of the futile cycle [27].…”

An In Vitro Bovine Cellular Model for Human Schlemm's Canal Endothelial Cells and Their Response to TGFβ Treatment

“…31 For consistent expression profiling, we examined the gene expression response of TGFβ2 treatment in SC cells using Bio-Rad ddPCR assays as previously described. 30,[32][33][34][35][36][37] All of the ddPCR assays are listed in Table 2.…”

Rapid stimulation of cellular Pi uptake by the inositol pyrophosphate InsP8induced by its photothermal release from lipid nanocarriers using a near infra-red light-emitting diode

“…Consequently, it now becomes plausible to consider that perturbation of Pi homeostasis (which unbalances countless metabolic processes 54 ), offers a mechanistic basis by which excess 1,5-InsP 8 production is associated with the deafness and keratoconus phenotypes that have been linked to certain PPIP5K missense mutations. 55,56 It is also notable that the addition to PPIP5K KO cells of 30-40 ml mL À1 of liposomes that contained 1,5-InsP 8 restored the degree of Pi uptake to the level observed for untreated WT cells The fluorescence in the gel was captured by using a GelDocXR+ (Bio-Rad). (B) Liposomes (200 mg mL À1 ) were added to cultures of HCT116 cells (1 Â 10 4 per well) for 4 h and then cells were washed twice and fresh culture medium was added prior to LED illumination (450 mW; 3 cm distance) for the indicated times.…”