The centrosomal protein nephrocystin-6 is mutated in Joubert syndrome and activates transcription factor ATF4.

The molecular basis of nephronophthisis, the most frequent genetic cause of renal failure in children and young adults, and its association with retinal degeneration and cerebellar vermis aplasia in Joubert syndrome are poorly understood. Using positional cloning, we here identify mutations in the gene CEP290 as causing nephronophthisis. It encodes a protein with several domains also present in CENPF, a protein involved in chromosome segregation. CEP290 (also known as NPHP6) interacts with and modulates the activity of ATF4, a transcription factor implicated in cAMP-dependent renal cyst formation. NPHP6 is found at centrosomes and in the nucleus of renal epithelial cells in a cell cycle-dependent manner and in connecting cilia of photoreceptors. Abrogation of its function in zebrafish recapitulates the renal, retinal and cerebellar phenotypes of Joubert syndrome. Our findings help establish the link between centrosome function, tissue architecture and transcriptional control in the pathogenesis of cystic kidney disease, retinal degeneration, and central nervous system development.

Paralysis of accommodation with preserved pupillary function as the initial manifestation of Guillain-Barré syndrome.

A 7-year-old boy who complained of blurred reading vision was found on ophthalmologic examination to have subnormal distance visual acuity in both eyes and a hyperopic refractive error that was deemed too small to explain his symptoms. Within days, he developed speech and gait deficits that led to a diagnosis of Guillain-Barré syndrome (GBS). Inpatient examination confirmed a profound binocular loss of accommodation with preservation of iris sphincter function and eye movements. This is only the second detailed report of accommodative loss with sparing of the pupil as the initial clinical manifestation of GBS.

The proneural basic helix-loop-helix gene ascl1a is required for retina regeneration.

Unlike mammals, teleost fish can regenerate an injured retina, restoring lost visual function. Little is known of the molecular events that underlie retina regeneration. We previously found that in zebrafish, retinal injury stimulates Müller glia to generate multipotent alpha1-tubulin (alpha1T) and pax6-expressing progenitors for retinal repair. Here, we report the identification of a critical E-box in the alpha1T promoter that mediates transactivation by achaete-scute complex-like 1a (ascl1a) during retina regeneration. More importantly, we show that ascl1a is essential for retina regeneration. Within 4 h after retinal injury, ascl1a is induced in Müller glia. Knockdown of ascl1a blocks the induction of alpha1T and pax6 as well as Müller glial proliferation, consequently preventing the generation of retinal progenitors and their differentiated progeny. These data suggest ascl1a is required to convert quiescent Müller glia into actively dividing retinal progenitors, and that ascl1a is a key regulator in initiating retina regeneration.

A role for alpha1 tubulin-expressing Müller glia in regeneration of the injured zebrafish retina.

Alpha1 tubulin (alpha1T) is a neuron-specific microtubule protein whose expression is induced in the developing and regenerating CNS. In the adult CNS, alpha1T expression remains high in neural progenitors. Transgenic zebrafish harboring a 1.7 kb alpha1T promoter fragment along with the first exon and intron express the transgene in a manner that recapitulates expression of the endogenous gene. We recently showed that this promoter mediates gene induction in retinal ganglion cells during optic nerve regeneration and in a subset of Müller glia that proliferate after retinal injury (Senut et al., 2004). To further characterize these Müller glia, we generated transgenic fish harboring an alpha1T promoter fragment that is specifically induced in these cells after retinal damage. Transgene expression, bromodeoxyuridine (BrdU) labeling, and stem cell marker expression suggested that alpha1T-expressing Müller glia dedifferentiate and become multipotent in response to injury. In addition, green fluorescent protein and BrdU-mediated lineage tracing combined with retinal gene expression analysis indicated that alpha1T-expressing Müller glia were capable of generating retinal neurons and glia. These data strongly suggest alpha1T-expressing Müller glia dedifferentiate and mediate regeneration of the injured zebrafish retina.

Impact of a Dedicated Research Rotation during Ophthalmology Residency.

BACKGROUND: The Accreditation Council for Graduate Medical Education (ACGME) requires that ophthalmology residents participate in scholarly activity during residency. However, residents lack protected time for research. OBJECTIVE: To determine the impact of a dedicated research rotation on scholarly productivity and research experience during residency. METHODS: This cohort study compared two groups of ophthalmology residents. Residents who graduated between 2004-2009 did not have dedicated research time and served as control residents (CR) while residents who graduated between 2010-2015 had a dedicated research rotation and served as the intervention group (research residents, RR). Primary outcomes included publications and presentations recorded over a four-year period, spanning the three years of residency and first year after graduation. These were analyzed by linear regression and t-tests. Residents also took surveys regarding research experience and chi squared tests and logistic regression were used to compare these results. RESULTS: The RR had 0.97 more publications and 1.3 more presentations compared to the CR after adjusting for PhD status, pre-residency publications and presentations, age at graduation, gender and race (p=0.09 and p=0.02, respectively). RR had higher odds of reporting adequate time to complete research (OR=13.11, 95% CI 3.58-48.03, p < 0.001) and satisfaction with their research experience (OR=6.96, 95% CI=2.104-23.053, p=0.002). CONCLUSIONS: Residents with a research rotation had more time to complete research, were more satisfied with their research experience, and generated more publications and presentations compared to residents without the research rotation. A research rotation can help meet ACGME requirements and help residents achieve greater scholarly activity.

Ascl1a regulates Müller glia dedifferentiation and retinal regeneration through a Lin-28-dependent, let-7 microRNA signalling pathway.

Unlike mammals, teleost fish mount a robust regenerative response to retinal injury that culminates in restoration of visual function. This regenerative response relies on dedifferentiation of Müller glia into a cycling population of progenitor cells. However, the mechanism underlying this dedifferentiation is unknown. Here, we report that genes encoding pluripotency factors are induced following retinal injury. Interestingly, the proneural transcription factor, Ascl1a, and the pluripotency factor, Lin-28, are induced in Müller glia within 6 h following retinal injury and are necessary for Müller glia dedifferentiation. We demonstrate that Ascl1a is necessary for lin-28 expression and that Lin-28 suppresses let-7 microRNA (miRNA) expression. Furthermore, we demonstrate that let-7 represses expression of regeneration-associated genes such as, ascl1a, hspd1, lin-28, oct4, pax6b and c-myc. hspd1, oct4 and c-myc(a) exhibit basal expression in the uninjured retina and let-7 may inhibit this expression to prevent premature Müller glia dedifferentiation. The opposing actions of Lin-28 and let-7 miRNAs on Müller glia differentiation and dedifferentiation are similar to that of embryonic stem cells and suggest novel targets for stimulating Müller glia dedifferentiation and retinal regeneration in mammals.