FMRpolyG accumulates in FMR1 premutation granulosa cells

Background

Fragile X premutation (Amplification of CGG number 55–200) is associated with increased risk for fragile X-Associated Premature Ovarian Insufficiency (FXPOI) in females and fragile X-associated tremor/ataxia syndrome (FXTAS) predominantly in males. Recently, it has been shown that CGG repeats trigger repeat associated non-AUG initiated translation (RAN) of a cryptic polyglycine-containing protein, FMRpolyG. This protein accumulates in ubiquitin-positive inclusions in neuronal brain cells of FXTAS patients and may lead to protein-mediated neurodegeneration. FMRpolyG inclusions were also found in ovary stromal cells of a FXPOI patient. The role of FMRpolyG expression has not been thoroughly examined in folliculogenesis related cells. The main goal of this study is to evaluate whether FMRpolyG accumulates in mural granulosa cells of FMR1 premutation carriers. Following FMRpolyG detection, we aim to examine premutation transfected COV434 as a suitable model used to identify RAN translation functions in FXPOI pathogenesis.

Results

FMRpolyG and ubiquitin immunostained mural granulosa cells from six FMR1 premutation carriers demonstrated FMRpolyG aggregates. However, co-localization of FMRpolyG and ubiquitin appeared to vary within the FMR1 premutation carriers’ group as three exhibited partial ubiquitin and FMRpolyG double staining and three premutation carriers demonstrated FMRpolyG single staining. None of the granulosa cells from the five control women expressed FMRpolyG. Additionally, human ovarian granulosa tumor, COV434, were transfected with two plasmids; both expressing 99CGG repeats but only one enables FMRpolyG expression. Like in granulosa cells from FMR1 premutation carriers, FMRpolyG aggregates were found only in COV434 transfected with expended CGG repeats and the ability to express FMRpolyG.

Conclusions

Corresponding with previous studies in FXTAS, we demonstrated accumulation of FMRpolyG in mural granulosa cells of FMR1 premutation carriers. We also suggest that following further investigation, the premutation transfected COV434 might be an appropriate model for RAN translation studies. Detecting FMRpolyG accumulation in folliculogenesis related cells supports previous observations and imply a possible common protein-mediated toxic mechanism for both FXPOI and FXTAS.

Lack of association of the WRN C1367T polymorphism with senile cataract in the Israeli population

PURPOSE

Werner syndrome is an autosomal recessive disease of premature aging caused by a polymorphic C1367T mutation in the Werner (WRN) gene. Although there are differences between the pathobiology of normal aging and the phenotype of Werner syndrome, the clinical age-related changes are similar. The aim of the study was to investigate the incidence of the C1367T (rs1346044) polymorphism in patients with age-related cataract.

METHODS

The study group consisted of 81 patients with senile cataract undergoing cataract extraction surgery. Data on age, sex, and medical history of microvascular disease and cancer were obtained from the medical files. Anterior lens capsule material was collected during surgery. DNA was extracted, amplified by polymerase chain reaction, and screened for the C1367T polymorphism in WRN using restriction enzymes followed by sequencing.

RESULTS

There were 33 male and 48 female patients of mean age 74.3+/-9 years. Genotypic frequencies were 67% for TT and 33% for TC. None of the patients had the CC genotype. Ten patients had a history of myocardial infarct, 8 cerebrovascular accident, and 8 various tumors. The distribution of these morbidities was similar in the two genotype groups.

CONCLUSIONS

The distribution of the C1367T WRN polymorphism in patients with senile cataract is similar to that in the normal population. Cataract formation in the elderly is not linked to a WRN mutation.

Progressive damage along the optic nerve following induction of crush injury or rodent anterior ischemic optic neuropathy in transgenic mice

PURPOSE

To characterize the histological changes that occur in response to induction of ischemic or mechanical optic nerve damage in transgenic mice.

METHODS

Either optic nerve crush injury or rodent anterior ischemic optic neuropathy (rAION) were induced in the right eye of mice transgenic for the Thy1 gene promoter expressing cyan fluorescent protein (CFP; n=40) and mice transgenic for the cyclic nucleotide phosphodiesterase (CNPase) gene promoter expressing green fluorescent protein (GFP; n=40). The left eye served as a control. The mice were euthanized at different times after injury. Eyes were enucleated, and the brain together with the optic nerves was completely dissected. Cryopreserved sections of both optic nerves were analyzed by fluorescence microscopy. In addition, flat-mounted retinas from the Thy1-CFP mice were analyzed for retinal ganglion cell (RGC) loss.

RESULTS

Axonal loss was detected in the right eye of the Thy1-CFP mice, and demyelination was detected in the CNPase-GFP mice. Both processes occurred simultaneously in the two models of injury. The damage proceeded retrogradely and, in the crush-injury group, crossed the chiasm within 4 days. At 21 days after injury, RGC loss measured 70% in the crush-injury group and 25% in the rAION group.

CONCLUSIONS

Axonal injury and demyelination along the optic nerves occur simultaneously in transgenic mice exposed to ischemic or crush injury. The degree of RGC loss reflects the severity of the injury. Loss of oligodendrocytes and myelin apparently leads to axonal loss. Transgenic mice offer a promising model for exploring the damage caused by optic nerve injury. Use of fluorescence labeling makes it possible to better understand the underlying pathophysiology, which can help researchers formulate neuroprotective agents.