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Retinal detachment is an important cause of visual loss. Currently, surgical techniques, including vitrectomy, scleral buckle, and pneumatic retinopexy, are the only means to repair retinal detachment and restore vision. However, surgical failure rates may be as high as 20%, and visual outcomes continue to vary secondary to multiple processes, including postoperative cystoid macular edema, epiretinal membrane formation, macular folds, and, ultimately, photoreceptor death. Therefore, pharmacotherapies are being sought to aid the success rates of modern surgical techniques and reduce or slow the degeneration of photoreceptors during retinal detachment. This review discusses potential therapeutic avenues that aid in retinal reattachment, reduce the rate of retinal redetachment by limiting proliferative vitreoretinopathy, and protect against photoreceptor cell death., (Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Purpose: To report the anatomic and functional recovery of the ellipsoid zone in a case of acute idiopathic blind spot enlargement (AIBSE), which was documented by serial high-resolution optical coherence tomography imaging., Observations: The patient's clinical presentation and follow up visits were documented via Humphrey's Visual Fields, fundus autofluorescence, and high resolution spectral domain optical coherence tomography (SD-OCT). At presentation, Humphrey's Visual Field testing showed an enlarged blind spot in the right eye. Fundus autofluorescence and optical coherence tomography showed an increased peripapillary autofluorescence and loss of the outer retinal layers, respectively. At 3 months a modest improvement in the visual field was observed. This improvement was stable at both the 7 and the 15 month follow up visits. SD-OCT corresponding to the areas of visual field improvement demonstrated recovery of the outer retina., Conclusion and Importance: Serial OCT imaging demonstrated anatomic evidence of ellipsoid zone recovery in isolated AIBSE. Anatomic recovery was consistent with the functional gain detected by visual field improvement.

The authors describe the first report in the literature of central retinal artery occlusion as the presenting manifestation of sarcoidosis. A 33-year-old man with asthma, headache, and 6 days of intermittent, transient vision loss in the OS presented with persistent vision loss in the OS. Ophthalmic examination was consistent with diagnosis of central retinal artery occlusion in the OS. Vascular imaging with CT angiography revealed an incidental finding of an intraconal mass surrounding the left optic nerve and hilar lymphadenopathy. Broncho scopic lymph node biopsy demonstrated noncaseating granulomas consistent with sarcoidosis. This case proffers a unique mechanism of vision loss in sarcoidosis and highlights that atypical causes of central retinal artery occlusion must be considered in patients without typical risk factors.

Purpose: To determine if (1) tortuosity assessment by a computer program (ROPtool, developed at the University of North Carolina, Chapel Hill, and Duke University, and licensed by FocusROP) that traces retinal blood vessels and (2) assessment by a lay reader are comparable with assessment by a panel of 3 retinopathy of prematurity (ROP) experts for remote clinical grading of vascular abnormalities such as plus disease., Design: Validity and reliability analysis of diagnostic tools., Participants: Three hundred thirty-five fundus images of prematurely born infants., Methods: Three hundred thirty-five fundus images of prematurely born infants were obtained by neonatal intensive care unit nurses. A panel of 3 ROP experts graded 84 images showing vascular dilatation, tortuosity, or both and 251 images showing no evidence of vascular abnormalities. These images were sent electronically to an experienced lay reader who independently graded them for vascular abnormalities. The images also were analyzed using the ROPtool, which assigns a numerical value to the level of vascular abnormality and tortuosity present in each of 4 quadrants or sectors. The ROPtool measurements of vascular abnormalities were graded and compared with expert panel grades with a receiver operating characteristic (ROC) curve. Grades between human readers were cross-tabulated. The area under the ROC curve was calculated for the ROPtool, and sensitivity and specificity were computed for the lay reader., Main Outcome Measures: Measurements of vascular abnormalities by ROPtool and grading of vascular abnormalities by 3 ROP experts and 1 experienced lay reader., Results: The ROC curve for ROPtool's tortuosity assessment had an area under the ROC curve of 0.917. Using a threshold value of 4.97 for the second most tortuous quadrant, ROPtool's sensitivity was 91% and its specificity was 82%. Lay reader sensitivity and specificity were 99% and 73%, respectively, and had high reliability (κ, 0.87) in repeated measurements., Conclusions: ROPtool had very good accuracy for detection of vascular abnormalities suggestive of plus disease when compared with expert physician graders. The lay reader's results showed excellent sensitivity and good specificity when compared with those of the expert graders. These options for remote reading of images to detect vascular abnormalities deserve consideration in the quest to use telemedicine with remote reading for efficient delivery of high-quality care and to detect infants requiring bedside examination., (Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Bilateral cases of branch retinal vein occlusions (BRVO) are infrequent and often related to systemic disease. A 72-year-old man with biochemical recurrence of prostate cancer was referred for decreased vision in his left eye. Fundus examination and fluorescein angiography disclosed bilateral BRVO with patches of peripheral non-perfusion and macular oedema in the left eye. A systemic work up revealed elevated fibrinogen and reduced free protein S antigen, consistent with an underlying hypercoagulable state. Cancer is a well-known cause of hypercoagulability. We report the first case of bilateral BRVO related to biochemical recurrence of prostate cancer and a proven coagulation derangement., (2015 BMJ Publishing Group Ltd.)

A 42-year-old man presented with 3 weeks of blurry vision in the right eye. His exam was significant for decreased vision in the right eye, diffuse retinopathy in both eyes, and serous retinal detachment in the right eye. The patient was found to be hypertensive with blood pressure of 256/160 mmHg. He was diagnosed with hypertensive emergency with end-organ damage due to features of hypertensive chorioretinopathy. He was admitted with abnormal urinalysis, elevated troponin, and abnormal EKG. After appropriate control of his blood pressure, his vision and his labs normalized. Hypertensive emergencies can be manifested first in the eyes. When the choroid is associated, the hypertensive event is often more acute and associated with increased morbidity. It is imperative to obtain a fundus exam in any patient with elevated blood pressure and concomitant vision complaints.

Purpose: To determine risk factors associated with development of a branch retinal vein occlusion (BRVO) among a large group of managed-care plan beneficiaries in the United States., Design: Retrospective, longitudinal cohort study., Participants: All beneficiaries age ≥55 years continuously enrolled for ≥2 years in a managed care network from 2001-2009 who had ≥2 visits to an eye care provider., Methods: Multivariable Cox regression analyses identified sociodemographic factors, ocular and nonocular conditions associated with incident BRVO., Main Outcome Measures: Hazard of incident BRVO with 95% confidence interval (CI)., Results: Of the 492,488 enrollees who met inclusion criteria, 2283 (0.5%) developed incident BRVO. After adjustment for confounding factors, blacks (adjusted hazard ratio [aHR], 1.43; CI, 1.19-1.73; P = 0.0001) had a 43% increased hazard of BRVO relative to non-Hispanic whites. Enrollees with hypertension (HTN) alone (aHR, 1.78; CI, 1.36-2.32; P < 0.0001) or HTN along with other metabolic syndrome components (diabetes mellitus [DM] and hyperlipidemia; aHR, 1.44; CI, 1.12-1.84; P = 0.005) had an increased hazard of developing a BRVO compared with those with none of these conditions. Disease severity was important; enrollees with end-organ damage caused by HTN had a 107% increased hazard of developing BRVO compared with enrollees without HTN (aHR, 2.07; CI, 1.75-2.45; P < 0.0001). Although there was no association between DM without end-organ damage and BRVO (aHR, 0.92; CI, 0.81-1.04; P = 0.2), individuals with end-organ damage from DM had a 36% increased hazard of BRVO (aHR, 1.36; CI, 1.18-1.57; P < 0.0001) compared with those without DM. Although cerebrovascular accident was associated with an increased hazard of developing BRVO (aHR, 1.34; CI, 1.19-1.52; P < 0.0001), other diseases of the vascular system (deep venous thrombosis/pulmonary embolism, peripheral vascular disease, hypercoagulable state, myocardial infarction) or anticoagulant use did not increase the risk of BRVO (P > 0.10 for all comparisons)., Conclusions: Both HTN and end-organ damage from DM contribute to arteriosclerosis, atherosclerosis, and endothelial dysfunction, which seem to be major risk factors for BRVO. Ophthalmologists should emphasize to patients and their primary physicians the importance of effectively managing systemic medical conditions associated with BRVO., (Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Purpose of Review: Retinal cell death is the main cause of vision loss in many blinding conditions. Research on the basics of how and why retinal cells die in different diseases provides insights into the development of treatment strategies to prevent or reverse this loss. This review summarizes the literature published on this topic in the last year., Recent Findings: Apoptosis is generally considered the main pathway by which retinal cells die in response to a range of noxious stimuli. However, inhibiting apoptosis does not completely prevent retinal cell death, as many enter programmed necrosis or necroptosis. Many novel ways of inhibiting apoptosis and necrosis, including blockage of the Fas receptor, neuroprotective peptides and antioxidants, continue to be investigated. Also, additional pathways including autophagy and inflammation are being examined on how they contribute to the loss of retinal cells in different disease models., Summary: With more knowledge of how retinal cells die, further advances are being made in prolonging the cell survival. However, even as basic science discoveries remain promising, clinical utility of neuroprotection is still quite limited at this time.

Purpose: To describe immunogammopathy maculopathy in the setting of Waldenström macroglobulinemia and its lack of response to ocular treatment., Methods: Case report of a 65-year-old male patient who presented with a 4-month history of progressive vision loss in the left eye., Results: Initial ophthalmic examination showed bilateral central retinal vein occlusion with macular edema, including serous macular detachment in the left eye. Serum protein electrophoresis revealed elevated IgM levels, leading to a diagnosis of Waldenström macroglobulinemia. The patient underwent plasmapheresis and systemic chemotherapy with improvement of hyperviscosity retinopathy. However, the macular detachment and edema in the left eye persisted despite repeated intravitreal injections of bevacizumab. Panretinal photocoagulation and intravitreal corticosteroid treatment were also unsuccessful in reversing the maculopathy. A diagnosis of immunogammopathy maculopathy was made, and partial improvement was seen over time after the treatment of Waldenström macroglobulinemia., Conclusion: In the setting of systemic immunogammopathy, conventional treatments for macular edema, including intravitreal anti-vascular endothelial growth factor agents and corticosteroids, may be ineffective. Ocular involvement responds to systemic chemotherapy and plasmapheresis directed against the underlying hematologic malignancy, although this response may be slow and incomplete.

Background: The purpose of this case report is to describe clinical and angiographic findings of retinal vasculitis in acute Toxocara canis neuroretinitis associated with systemic infection., Findings: A 16-year-old male presented with a 1 week history of left eye pain, floaters, and decreased visual acuity. Ocular examination was consistent with neuroretinitis and retinal vasculitis. Fluorescein angiography demonstrated leakage of fluorescein from the optic nerve and the retinal veins. Clinical and laboratory evaluation were consistent with systemic Toxocara canis infection., Conclusions: Ocular T. canis may present with retinal vasculitis in young patients in the setting of acute systemic infection.

Aim: To propose a new mechanism for the development of idiopathic macular hole in the setting of pre-existing posterior vitreous detachment (PVD)., Methods: Patients were examined clinically with fundus contact lens biomicroscopy and high-definition optical coherence tomography (OCT) was used to characterize the structural changes in the fovea following PVD., Results: Two patients presented with vitreofoveal separation and were found by high-definition OCT to have subtle foveal disruption and irregularity of the foveal contour with no evidence of a full thickness macular hole. Sequential examination of these patients demonstrated delayed formation of idiopathic macular hole., Conclusion: Traction-induced inner foveal damage occurring before or coincident with spontaneous vitreofoveal separation destabilizes the fovea and predisposes some eyes to delayed macular hole formation.

In this study, we examined the role of Fas apoptotic inhibitory molecule 2 (Faim2), an inhibitor of the Fas signaling pathway, and its regulation by stress kinase signaling during Fas-mediated apoptosis of 661W cells, an immortalized photoreceptor-like cell line Treatment of 661W cells with a Fas-activating antibody led to increased levels of Faim2. Both ERK and JNK stress kinase pathways were activated in Fas-treated 661W cells, but only the inhibition of the ERK pathway reduced the levels of Faim2. Blocking the ERK pathway using a pharmacological inhibitor increased the susceptibility of 661W cells to Fas-induced caspase activation and apoptosis. When the levels of Faim2 were reduced in 661W cells by siRNA knockdown, Fas activating antibody treatment resulted in earlier and more robust caspase activation, and increased cell death. These results demonstrate that Faim2 acts as a neuroprotectant during Fas-mediated apoptosis of 661W cells. The expression of Faim2 is triggered, at least in part, by Fas-receptor activation and subsequent ERK signaling. Our findings identify a novel protective pathway that auto-regulates Fas-induced photoreceptor apoptosis in vitro. Modulation of this pathway to increase Faim2 expression may be a potential therapeutic option to prevent photoreceptor death.

In accelerated hypertension, vasogenic brain edema associated with PRES may represent either autoregulatory breakthrough leading to vasodilation or excessive autoregulation leading to vasoconstriction. We describe 2 patients with PRES in accelerated hypertension who had serous retinal detachments, a vasoconstrictive phenomenon. The concurrence of serous retinal detachment and PRES offers intriguing support for the idea that vasoconstriction rather than vasodilation is the mechanism of vasogenic edema in PRES.

Purpose: To examine the activation of autophagy and its relationship to Fas-mediated photoreceptor apoptosis during experimental retinal detachment., Methods: Retina-retinal pigment epithelium (RPE) separation was created in Brown-Norway rats by subretinal injection of 1% hyaluronic acid and the intraretinal levels of the autophagy proteins LC3 and Atg5, the time course of LC3-I to LC3-II conversion, and the activation of cathepsins B and D were assayed with Western blot analysis and immunohistochemistry. We measured the ability of a Fas-activating antibody to induce LC3-I to LC3-II conversion in 661W cells, and the in vivo effect of Met12, a small molecule inhibitor of the Fas receptor, on LC3-I to LC3-II conversion and Atg5 expression. Autophagy activation was inhibited using 3-methyladenine (3-MA) or siRNA knockdown of Atg5 and the effect on apoptosis was measured using a caspase 8 activity assay, caspase 8 immunoblots, and photoreceptor TUNEL staining., Results: Retina-RPE separation resulted in a Fas-dependent activation of autophagy, with increased Atg5 levels and intraphotoreceptor conversion of LC3-I to LC3-II. Detached retinas had increased levels of autophagosome-associated lysosomal proteases, cathepsins B and D. Inhibition of autophagy by 3-MA or siAtg5 accelerated the time course of caspase 8 activation and photoreceptor TUNEL staining., Conclusions: Autophagy activation occurs in the photoreceptors after retina-RPE separation. This appears to be, at least in part, dependent on Fas receptor activation, and plays a role in regulating the level of photoreceptor apoptosis.

Aim: To report a case of pseudoxanthoma elasticum (PXE) in a 48 year old woman that presented with bilateral blurry vision., Methods: A case report, Results: A 48-year-old woman presented with bilateral blurry vision and right eye metamorphopsia. The patient had a history of angioid streaks in the left eye ten years ago for which she had received laser surgery and had poor residual vision. Visual acuity was 20/60 in the right eye and count fingers at 6 feet in the left. Fundus examination showed subretinal hemorrhage and macular thickening on the right and a disciform macular scar with focal atrophic pigment epithelial lesions on the left. Both eyes had angioid streaks and peau d'orange pigmentary pattern of the retina. External examination showed several, yellow skin papules and plaques on the lateral and posterior neck, as well as prominent mental creases. Pathologic examination of skin biopsy confirmed the diagnosis of PXE, showing calcium deposition and fragmented, clumped elastic fibers in the deep reticular dermis. She responded well to intravitreal bevacizumab injections and visual acuity improved to 20/25 OD. Preventative care was emphasized and the patient was referred to cardiology, gastroenterology and human genetics for counseling., Conclusion: PXE is a multisystem disorder affecting the dermatologic, ocular, and cardiovascular systems. Ophthalmic findings of angioid streaks and choroidal neovascularization in the presence of stereotypical skin changes and prominent mental creases should prompt evaluation for PXE.

Bilateral diffuse uveal melanocytic proliferation is a rare paraneoplastic syndrome that presents with bilateral progressive loss of vision. A 70-year-old woman presented with a 3-month history of progressive, bilateral vision loss. The patient had bilateral, diffuse, shallow, subretinal fluid with patchy, reddish-brown lesions at the level of the retinal pigment epithelium (RPE) that showed significant early hyperfluorescence on fluorescein angiography and a corresponding loss of autofluorescence. Optical coherence tomography of both eyes revealed complete RPE and inner segment/outer segment junction loss with adjacent areas of thickening at the level of the RPE. Bilateral diffuse uveal melanocytic proliferation was diagnosed based on these clinical findings, and a systemic evaluation for malignancy revealed metastatic endometrial adenocarcinoma. Both autofluorescence and optical coherence tomography demonstrated unique imaging characteristics that correlated with the reported histopathology of bilateral diffuse uveal melanocytic proliferation. These imaging modalities can contribute to the rapid and accurate diagnosis of bilateral diffuse uveal melanocytic proliferation., (Copyright 2010, SLACK Incorporated.)

Purpose. To test the effect of a small peptide inhibitor (Met12) of the Fas receptor on the activation of extrinsic and intrinsic apoptosis pathways after retinal detachment. Methods. Retinal-RPE separation was created in Brown Norway rats by subretinal injection of 1% hyaluronic acid. Met12, derived from the Fas-binding extracellular domain of the oncoprotein Met, was injected into the subretinal space at the time of separation. A mutant peptide and vehicle administered in a similar fashion acted as inactive controls. The extrinsic apoptotic pathway was induced in 661W cells using a Fas-activating antibody in the presence or absence of Met12. Caspase 3, caspase 8, and caspase 9 activities were measured with calorimetric and luminescent assays in retinal extracts and cell lysates. Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) was performed in retinal sections 3 days after separation. Histology was performed in retinal sections 2 months after retinal detachment. Results. Met12 inhibited Fas-induced caspase 8 activation in 661W cells. Similarly, administration of Met12 into the subretinal space inhibited the activation of caspase 3, caspase 8, and caspase 9 after retinal detachment. This corresponded to a decreased level of TUNEL-positive staining of photoreceptors after retinal-RPE separation in animals that received Met12, but not inactive mutant, peptide treatment. After 2 months, the outer nuclear layer was significantly thicker, and the photoreceptor count was higher in animals treated with subretinal Met12. Conclusions. The small peptide Met12 may serve as a photoreceptor-protective agent in the setting of retinal-RPE separation.

In neurons, DNA damage induces protein synthesis-dependent apoptosis mediated by the mitochondrial intrinsic cell-death pathway. Signal transduction cascades activated by genotoxic stress upstream of the mitochondria are largely unknown. We identified protein kinase D (PKD) as one of the earliest markers of neuronal DNA damage. Phosphorylation of the PKD-activation domain could be detected within 15 min of genotoxic stress and was concurrent with ataxia telangiectasia-mutated (ATM) activation. PKD stimulation was selective to DNA damage and did not occur with other stress stimuli examined. In vivo, both young and adult rats showed increased levels of phosphorylated PKD in neuronal tissues after injection of DNA-toxin etoposide. These results indicate that PKD activation is an early neuronal response to DNA damage, suggesting that signaling downstream of PKD may be critical for neuronal survival after genotoxic stress.

c-Jun is induced in many neuronal death paradigms. A critical step in c-Jun regulation involves phosphorylation of Ser63/Ser73 located in the NH2-terminal transactivation domain. To determine the importance of this phosphorylation for neuronal apoptosis, we analyzed the sympathetic neurons of mice carrying a mutant c-Jun gene that lacks Ser63/Ser73 phosphorylation sites (jun aa). Trophic factor-deprivation or DNA damage-induced death was significantly delayed in jun aa/aa neurons. Neuronal c-Jun induction was only partially inhibited, demonstrating that phosphorylation of Ser63/73 is not required for c-Jun activation. The inductions of proapoptotic BH3-only proteins, Bim and PUMA/Bbc3, were delayed during neuronal apoptosis in mutant neurons. These results demonstrate that NH2-terminal c-Jun phosphorylation is important, but not necessary, for the induction of proapoptotic genes and neuronal apoptosis. Thus, additional JNK substrates may be critical for neuronal death. As potential mediators, we identified additional nuclear MLK/JNK substrates, including Nup214 subunit of the nuclear pore complex.

The activation of the c-Jun N-terminal kinase (JNK) pathway is critical for naturally occurring neuronal cell death during development and may be important for the pathological neuronal cell death of neurodegenerative diseases. The small molecule inhibitor of the mixed-lineage kinase (MLK) family of kinases, CEP-1347, inhibits the activation of the JNK pathway and, consequently, the cell death in many cell culture and animal models of neuronal death. CEP-1347 has the ability not only to inhibit cell death but also to maintain the trophic status of neurons in culture. The possible importance of the JNK pathway in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases provides a rationale for the use of CEP-1347 for the treatment of these diseases. CEP-1347 has the potential of not only retarding disease progression but also reversing the severity of symptoms by improving the function of surviving neurons.

Cytosine arabinoside (ara-C) is a nucleoside analog used in the treatment of hematologic malignancies. One of the major side effects of ara-C chemotherapy is neurotoxicity. In this study, we have further characterized the cell death induced by ara-C in sympathetic neurons. Similar to neurons undergoing trophic factor deprivation-induced apoptosis, ara-C-exposed neurons became hypometabolic before death and upregulated c-myb, c-fos, and Bim. Bax deletion delayed, but did not prevent, ara-C toxicity. Neurons died by apoptosis, indicated by the release of mitochondrial cytochrome-c and caspase-3 activation. p53-deficient neurons demonstrated decreased sensitivity to ara-C, but neither p53 nor multiple p53-regulated genes were induced. Mature neurons showed increased ara-C resistance. These results demonstrate that molecular mechanisms underlying ara-C-induced death are similar to those responsible for trophic factor deprivation-induced apoptosis. However, substantial differences in neuronal death after these two distinct stress stimuli exist since ara-C toxicity, unlike the developmental death, can proceed in the absence of Bax.

Activation of the JNK pathway and induction of the AP-1 transcription factor c-Jun are critical for neuronal apoptosis caused by a variety of insults. Ara-C-induced DNA damage caused rapid sympathetic neuronal death that was associated with an increase of c-jun expression. In addition, c-Jun was phosphorylated in its N-terminal transactivation domain, which is important for c-Jun-mediated gene transcription. Blocking c-Jun activation by JNK pathway inhibition prevented neuronal death after stress. In contrast, neither the JNK inhibitor SP600125 nor the mixed lineage kinase inhibitor CEP-1347 prevented cytosine arabinoside-induced neuronal death, demonstrating that the JNK pathway was not necessary for DNA damage-induced neuronal apoptosis. Surprisingly, SP600125 or CEP-1347 could not block c-Jun induction or phosphorylation after DNA damage. Pharmacological inhibitors of cyclin-dependent kinase (CDK) activity completely prevented c-Jun phosphorylation after DNA damage. These results demonstrate that c-Jun activation during DNA damage-induced neuronal apoptosis was independent of the classical JNK pathway and was mediated by a novel c-Jun kinase. Based on pharmacological criteria, DNA damage-induced neuronal c-Jun kinase may be a member of the CDK family or be activated by a CDK-like kinase. Activation of this novel kinase and subsequent phosphorylation of c-Jun may be important in neuronal death after DNA damage.

Trophic factor deprivation (TFD) activates c-Jun N-terminal kinases (JNKs), culminating in coordinate AP1-dependent transactivation of the BH3-only BCL-2 proteins BIM(EL) and HRK, which in turn are critical for BAX-dependent cytochrome c release, caspase activation, and apoptosis. Here, we report that TFD caused not only induction but also phosphorylation of BIM(EL). Mitochondrially localized JNKs but not upstream activators, like mixed-lineage kinases (MLKs) or mitogen-activated protein kinase kinases (MKKs), specifically phosphorylated BIM(EL) at Ser65, potentiating its proapoptotic activity. Inhibition of the JNK pathway attenuated BIM(EL) expression, prevented BIM(EL) phosphorylation, and abrogated TFD-induced apoptosis. Conversely, activation of this pathway promoted BIM(EL) expression and phosphorylation, causing BIM- and BAX-dependent cell death. Thus, JNKs regulate the proapoptotic activity of BIM(EL) during TFD, both transcriptionally and posttranslationally.

Mammalian MACF1 (Macrophin1; previously named ACF7) is a giant cytoskeletal linker protein with three known isoforms that arise by alternative splicing. We isolated a 19.1-kb cDNA encoding a fourth isoform (MACF1-4) with a unique N-terminus. Instead of an N-terminal actin-binding domain found in the other three isoforms, MACF1-4 has eight plectin repeats. The MACF1 gene is located on human Chr 1p32, contains at least 102 exons, spans over 270 kb, and gives rise to four major isoforms with different N-termini. The genomic organization of the actin-binding domain is highly conserved in mammalian genes for both plectin and BPAG1. All eight plectin repeats are encoded by one large exon; this feature is similar to the genomic structure of plectin. The intron positions within spectrin repeats in MACF1 are very similar to those in the dystrophin gene. This demonstrates that MACF1 has characteristic features of genes for two classes of cytoskeletal proteins, i.e., plectin and dystrophin.

We isolated a full-length cDNA encoding a novel 278 amino acid beta subunit of Na,K-ATPase from a mouse retinal cDNA library. The highest sequence identity was to known beta 3 isoforms, identifying the protein as the mouse beta 3 subunit of Na,K-ATPase. Two transcripts, 1.75 kb and 2.1 kb, probably arise from use of alternative poly(A) addition signals.