Retinopathy of prematurity screening: prevalence and risk factors of ophthalmic complications in non-treated preterm infants.

INTRODUCTION: Retinopathy of prematurity (ROP) is a vision-threatening disease of premature infants. Practice guidelines recommend that all infants screened for ROP receive follow-up eye examinations to screen for ophthalmic complications.1 The purpose of this study was to identify risk factors for the development of strabismus, amblyopia, high refractive error, and cataracts among ROP-screened, non-treated infants. METHODS: Retrospective single-centre study of ROP-screened, non-treated premature infants with ophthalmic follow-up. Clinical variables were screened for association with ocular findings at follow-up. Multivariable logistic regression was used to determine the risk factors associated with ocular findings. RESULTS: 309 patients were seen for follow-up at 0.97 (0.69) [mean (SD)] years after neonatal intensive care unit (NICU) discharge. Strabismus was predicted by occipitofrontal circumference (OFC) z-score at NICU discharge (OR 0.61; 95% CI [0.42, 0.88]; p = 0.008), intraventricular haemorrhage (IVH) grade III or IV (OR 3.18; 95% CI [1.18, 8.54]; p = 0.02), and exclusive formula feeding at NICU discharge (OR 2.20; 95% CI [1.07, 4.53]; p = 0.03). Significant predictors of amblyopia were OFC z-score at discharge (OR 0.55; 95% CI [0.31, 0.96]; p = 0.03) and necrotising enterocolitis (NEC) (OR 6.94; 95% CI [1.38, 35.00]; p = 0.02). NEC was a significant risk factor for high refractive error (OR 7.27; 95% CI [1.39, 37.94]; p = 0.02). CONCLUSIONS: Among premature infants screened but not treated for ROP, severe IVH, NEC, low OFC z-score, and exclusive formula feeding at NICU discharge were risk factors for ocular morbidity. These findings affirm the value of ophthalmic follow-up for all ROP-screened infants, particularly those with the identified risk factors.

Severe Mpox Infection of the Eye and Periocular Region.

Mpox is an emerging zoonotic infection with potentially severe ocular and periocular consequences, particularly in immunocompromised patients. This report summarizes 2 cases of fulminant mpox presenting in patients with AIDS. In the first case, confluent lesions resulted in orbital compartment syndrome and total eyelid necrosis. In the second case, eyelid involvement was accompanied by corneal melt and perforation. Despite aggressive medical and surgical treatment, both patients developed permanent loss of vision and ultimately expired.

CHARGE syndrome protein CHD7 regulates epigenomic activation of enhancers in granule cell precursors and gyrification of the cerebellum.

Regulation of chromatin plays fundamental roles in the development of the brain. Haploinsufficiency of the chromatin remodeling enzyme CHD7 causes CHARGE syndrome, a genetic disorder that affects the development of the cerebellum. However, how CHD7 controls chromatin states in the cerebellum remains incompletely understood. Using conditional knockout of CHD7 in granule cell precursors in the mouse cerebellum, we find that CHD7 robustly promotes chromatin accessibility, active histone modifications, and RNA polymerase recruitment at enhancers. In vivo profiling of genome architecture reveals that CHD7 concordantly regulates epigenomic modifications associated with enhancer activation and gene expression of topologically-interacting genes. Genome and gene ontology studies show that CHD7-regulated enhancers are associated with genes that control brain tissue morphogenesis. Accordingly, conditional knockout of CHD7 triggers a striking phenotype of cerebellar polymicrogyria, which we have also found in a case of CHARGE syndrome. Finally, we uncover a CHD7-dependent switch in the preferred orientation of granule cell precursor division in the developing cerebellum, providing a potential cellular basis for the cerebellar polymicrogyria phenotype upon loss of CHD7. Collectively, our findings define epigenomic regulation by CHD7 in granule cell precursors and identify abnormal cerebellar patterning upon CHD7 depletion, with potential implications for our understanding of CHARGE syndrome.

Photoreceptor responses to light in the pathogenesis of diabetic retinopathy.

Vision loss, among the most feared complications of diabetes, is primarily caused by diabetic retinopathy, a disease that manifests in well-recognized, characteristic microvascular lesions. The reasons for retinal susceptibility to damage in diabetes are unclear, especially considering that microvascular networks are found in all tissues. However, the unique metabolic demands of retinal neurons could account for their vulnerability in diabetes. Photoreceptors are the first neurons in the visual circuit and are also the most energy-demanding cells of the retina. Here, we review experimental and clinical evidence linking photoreceptors to the development of diabetic retinopathy. We then describe the influence of retinal illumination on photoreceptor metabolism, effects of light modulation on the severity of diabetic retinopathy, and recent clinical trials testing the treatment of diabetic retinopathy with interventions that impact photoreceptor metabolism. Finally, we introduce several possible mechanisms that could link photoreceptor responses to light and the development of retinal vascular disease in diabetes. Collectively, these concepts form the basis for a growing body of investigative efforts aimed at developing novel pharmacologic and nonpharmacologic tools that target photoreceptor physiology to treat a very common cause of blindness across the world.

Chromatin Environment and Cellular Context Specify Compensatory Activity of Paralogous MEF2 Transcription Factors.

Compensation among paralogous transcription factors (TFs) confers genetic robustness of cellular processes, but how TFs dynamically respond to paralog depletion on a genome-wide scale in vivo remains incompletely understood. Using single and double conditional knockout of myocyte enhancer factor 2 (MEF2) family TFs in granule neurons of the mouse cerebellum, we find that MEF2A and MEF2D play functionally redundant roles in cerebellar-dependent motor learning. Although both TFs are highly expressed in granule neurons, transcriptomic analyses show MEF2D is the predominant genomic regulator of gene expression in vivo. Strikingly, genome-wide occupancy analyses reveal upon depletion of MEF2D, MEF2A occupancy robustly increases at a subset of sites normally bound to MEF2D. Importantly, sites experiencing compensatory MEF2A occupancy are concentrated within open chromatin and undergo functional compensation for genomic activation and gene expression. Finally, motor activity induces a switch from non-compensatory to compensatory MEF2-dependent gene regulation. These studies uncover genome-wide functional interdependency between paralogous TFs in the brain.

The Transcriptional Regulator SnoN Promotes the Proliferation of Cerebellar Granule Neuron Precursors in the Postnatal Mouse Brain.

Control of neuronal precursor cell proliferation is essential for normal brain development, and deregulation of this fundamental developmental event contributes to brain diseases. Typically, neuronal precursor cell proliferation extends over long periods of time during brain development. However, how neuronal precursor proliferation is regulated in a temporally specific manner remains to be elucidated. Here, we report that conditional KO of the transcriptional regulator SnoN in cerebellar granule neuron precursors robustly inhibits the proliferation of these cells and promotes their cell cycle exit at later stages of cerebellar development in the postnatal male and female mouse brain. In laser capture microdissection followed by RNA-Seq, designed to profile gene expression specifically in the external granule layer of the cerebellum, we find that SnoN promotes the expression of cell proliferation genes and concomitantly represses differentiation genes in granule neuron precursors in vivo Remarkably, bioinformatics analyses reveal that SnoN-regulated genes contain binding sites for the transcription factors N-myc and Pax6, which promote the proliferation and differentiation of granule neuron precursors, respectively. Accordingly, we uncover novel physical interactions of SnoN with N-myc and Pax6 in cells. In behavior analyses, conditional KO of SnoN impairs cerebellar-dependent learning in a delayed eye-blink conditioning paradigm, suggesting that SnoN-regulation of granule neuron precursor proliferation bears functional consequences at the organismal level. Our findings define a novel function and mechanism for the major transcriptional regulator SnoN in the control of granule neuron precursor proliferation in the mammalian brain.SIGNIFICANCE STATEMENT This study reports the discovery that the transcriptional regulator SnoN plays a crucial role in the proliferation of cerebellar granule neuron precursors in the postnatal mouse brain. Conditional KO of SnoN in granule neuron precursors robustly inhibits the proliferation of these cells and promotes their cycle exit specifically at later stages of cerebellar development, with biological consequences of impaired cerebellar-dependent learning. Genomics and bioinformatics analyses reveal that SnoN promotes the expression of cell proliferation genes and concomitantly represses cell differentiation genes in vivo Although SnoN has been implicated in distinct aspects of the development of postmitotic neurons, this study identifies a novel function for SnoN in neuronal precursors in the mammalian brain.