Biology subjects

Ubels, J. L.

Publications and source records attributed to Ubels, J. L..

4 recordsLinked to original sources

bioRxiv2021

Structure and Function of the Retina of Low-density Lipoprotein Receptor-related Protein 5 (Lrp5)-deficient Rats

Loss-of-function mutations in the Wnt co-receptor, low-density lipoprotein receptor-related protein 5 (LRP5), result in familial exudative vitreoretinopathy (FEVR), osteoporosis-pseudoglioma syndrome (OPPG), and Norrie disease. CRISPR/Cas9 gene editing was used to produce rat strains deficient in Lrp5. The purpose of this study was to validate this rat model for studies of hypovascular, exudative retinopathies. The retinal vasculature of wildtype and Lrp5 knockout rats was stained with Giffonia simplifolia isolectin B4 and imaged by fluorescence microscopy. Effects on retinal structure were investigated by histology. The integrity of the blood-retina barrier was analyzed by staining for claudin-5 and measurement of permeability to Evans blue dye. Retinas were imaged by fundus photography and SD-OCT, and electroretinograms were recorded. Lrp5 gene deletion led to sparse superficial retinal capillaries and loss of the deep and intermediate plexuses. Autofluorescent exudates were observed, correlated with absence of claudin-5 expression in superficial vessels and increased Evans blue permeability. OCT images show pathology similar to OCT of humans with FEVR, and retinal thickness is reduced by 50% compared to wild-type rats. Histology and OCT reveal that photoreceptor and outer plexiform layers are absent. The retina failed to demonstrate an ERG response. CRISPR/Cas9 gene-editing produced a predictable rat Lrp5 knockout model with extensive defects in the retinal vascular and neural structure and function. This rat model should be useful for studies of exudative retinal vascular diseases involving the Wnt and norrin pathways.

genetics↗

bioRxiv2020

Low-density Lipoprotein Receptor-related Protein 5 (LRP5)-deficient Rats Have Reduced Bone Mass and Abnormal Development of the Retinal Vasculature

Humans carrying homozygous loss-of-function mutations in the Wnt co-receptor LRP5 (low-density lipoprotein receptor-related protein 5) develop osteoporosis and a defective retinal vasculature known as familial exudative vitreoretinopathy (FEVR) due to disruption of the Wnt signaling pathway. The purpose of this study was to use CRISPR/Cas9-mediated gene editing to create strains of Lrp5-deficient rats and to determine whether knockout of Lrp5 resulted in phenotypes that model the bone and retina pathology in LRP5-deficient humans. Knockout of Lrp5 in rats produced low bone mass, decreased bone mineral density, and decreased bone size. The superficial retinal vasculature of Lrp5-deficient rats was sparse and disorganized, with extensive exudates and decreases in vascularized area, vessel length, and branch point density. This study showed that Lrp5 could be predictably knocked out in rats using CRISPR/Cas9, causing the expression of bone and retinal phenotypes that will be useful for studying the role of Wnt signaling in bone and retina development and for research on the treatment of osteoporosis and FEVR.

developmental biology↗

bioRxiv2019

Patch-Clamp Recording of K+ Current from Lacrimal Gland Duct Cells

Electrophysiologic studies have characterized ion channels in lacrimal gland acinar cells, but due to relative paucity and inaccessibility, such studies on lacrimal gland duct cells are challenging. The duct cells are believed to secrete the high level of K+ that is present in tears. The goal of this project was to develop a method for isolation of viable, single duct cells, demonstrate their utility for patch-clamp recording and characterize the K+ channels expressed by duct cells. Exorbital lacrimal gland slices from Sprague-Dawley rats were incubated with collagenase. Under a microscope, the ducts were microdissected from the glands and then incubated with elastase and collagenase. Dispersed duct cells were plated on a cover slip coated with BD Cell-Tak. Duct cells were distinguished from acinar cells by their smaller size and lack of granularity. Whole-cell K+ currents were recorded from duct cells using the perforated-patch technique and pipettes with resistances of less than 10 M{Omega}. EGTA and CaCl2 in the pipette solution were adjusted to give 1 uM free Ca++. When held at -80 mV, duct cells showed K+ currents that activated at command voltages near 0 mV and reached amplitudes near 1 nA at +100 mV. Currents reached peak amplitude less than 20 ms after depolarization and did not inactivate. These currents were inactivated by holding the cells at 0 mV. Currents were blocked reversibly by TEA in the presence of Ca2+, but were not blocked by TEA in the absence of Ca2+. Currents were not affected by clotrimazole (10 uM) or Ba2+ (5 mM). A method has been established for isolation and dissociation lacrimal gland duct cells for electrophysiologic studies. These cells express a voltage-activated K+ channel that is dependent on the presence of intracellular Ca2+ and may correspond to the IKCa1 channel expressed on the apical membranes of lacrimal gland ducts.

physiology↗

bioRxiv2019

Prevalence of Refractive Error and Need for Corrective Lenses in Medically Underserved Residents of Tijuana, Mexico

PurposeThe population of Tijuana, Mexico is growing rapidly, with a current official population estimate of 1.7 million. Nearly 80,000 people migrate to Tijuana each year, resulting in the rise of neighborhoods with substandard housing, lack of services and inadequate access to health care, including eye care. This study describes refractive errors and the need for corrective lenses among participants attending free clinics in these neighborhoods where they received free eye exams and glasses during January 2016. Methods: This is a retrospective observational chart review of de-identified data collected from intake forms that were filled out for each participant at the clinics. Subjects were self-selected in response to announcements in the neighborhoods where clinics were conducted. Subjects with presenting uncorrected visual acuity 20/30 OU or worse were examined with an autorefractor to measure spherical refractive error. Either prescription or reading glasses were then distributed to participants who had refractive errors. Epi Info, an open source program provided by the CDC, was used to analyze demographic, visual acuity and refractive error data. Results: Presenting visual acuity was evaluated in 1209 people. Of these patients, 70% had a visual acuity of 20/30 or worse. Only 23% of these patients had glasses. Among the patients who were given refractions, 13% had clinically significant myopia (-0.75 D or worse in at least one eye). In participants 20 years old and younger, only 8% had clinically significant myopia. Clinically significant hyperopia (+0.75 D or worse in at least one eye) was detected in 25% of participants. Astigmatism (-1.5 D or worse in at least one eye) was present in 18% of participants. Prescription glasses were given to 542 participants and 396 of these people received their first glasses. Reading glasses were given to 386 people. Among students only 15% presented at the clinics with glasses, while it was determined that 56% of student participants needed glasses. Conclusion: The high levels of uncorrected refractive error in this study suggest limited access to affordable eye care in neighborhoods where clinics were conducted. Prevalence of myopia among adolescents and young adults is increasing in many parts of the world. In contrast, a relatively high prevalence of hyperopia was observed in this age group in Tijuana. The data demonstrate an urgent need for eye care and correction of refractive error in the study group.

epidemiology↗