Sjögren-Larsson syndrome: a complex metabolic disease with a distinctive ocular phenotype

Unraveling the CLCC1 interactome: Impact of the Asp25Glu variant and its interaction with SigmaR1 at the Mitochondrial-Associated ER Membrane (MAM)

The endoplasmic reticulum (ER) plays an indispensable role in cellular processes, including maintenance of calcium homeostasis, and protein folding, synthesized and processing. Disruptions in these processes leading to ER stress and the accumulation of misfolded proteins can instigate the unfolded protein response (UPR), culminating in either restoration of balanced proteostasis or apoptosis. A key player in this intricate balance is CLCC1, an ER-resident chloride channel, whose essential role extends to retinal development, regulation of ER stress, and UPR. The importance of CLCC1 is further underscored by its interaction with proteins localized to mitochondria-associated endoplasmic reticulum membranes (MAMs), where it participates in UPR induction by MAM proteins. In previous research, we identified a p.(Asp25Glu) pathogenic CLCC1 variant associated with retinitis pigmentosa (RP) (CLCC1 hg38 NC_000001.11; NM_001048210.3, c.75C > A; UniprotKB Q96S66). In attempt to decipher the impact of this variant function, we leveraged liquid chromatography-mass spectrometry (LC-MS) to identify likely CLCC1-interacting proteins. We discovered that the CLCC1 interactome is substantially composed of proteins that localize to ER compartments and that the Asp25Glu variant results in noticeable loss and gain of specific protein interactors. Intriguingly, the analysis suggests that the CLCC1Asp25Glu mutant protein exhibits a propensity for increased interactions with cytoplasmic proteins compared to its wild-type counterpart. To corroborate our LC-MS data, we further scrutinized two novel CLCC1 interactors, Calnexin and SigmaR1, chaperone proteins that localize to the ER and MAMs. Through microscopy, we demonstrate that CLCC1 co-localizes with both proteins, thereby validating our initial findings. Moreover, our results reveal that CLCC1 co-localizes with SigmaR1 not merely at the ER, but also at MAMs. These findings reinforce the notion of CLCC1 interacting with MAM proteins at the ER-mitochondria interface, setting the stage for further exploration into how these interactions impact ER or mitochondria function and lead to retinal degenerative disease when impaired.

Aldehyde Dehydrogenase and Aldo-Keto Reductase Enzymes: Basic Concepts and Emerging Roles in Diabetic Retinopathy

Diabetic retinopathy (DR) is a complication of diabetes mellitus that can lead to vision loss and blindness. It is driven by various biochemical processes and molecular mechanisms, including lipid peroxidation and disrupted aldehyde metabolism, which contributes to retinal tissue damage and the progression of the disease. The elimination and processing of aldehydes in the retina rely on the crucial role played by aldehyde dehydrogenase (ALDH) and aldo-keto reductase (AKR) enzymes. This review article investigates the impact of oxidative stress, lipid-derived aldehydes, and advanced lipoxidation end products (ALEs) on the advancement of DR. It also provides an overview of the ALDH and AKR enzymes expressed in the retina, emphasizing their growing importance in DR. Understanding the relationship between aldehyde metabolism and DR could guide innovative therapeutic strategies to protect the retina and preserve vision in diabetic patients. This review, therefore, also explores various approaches, such as gene therapy and pharmacological compounds that have the potential to augment the expression and activity of ALDH and AKR enzymes, underscoring their potential as effective treatment options for DR.

Untargeted Metabolomic Analysis of Sjögren-Larsson Syndrome Reveals a Distinctive Pattern of Multiple Disrupted Biochemical Pathways

Sjögren-Larsson syndrome (SLS) is a rare inherited neurocutaneous disease characterized by ichthyosis, spastic diplegia or tetraplegia, intellectual disability and a distinctive retinopathy. SLS is caused by bi-allelic mutations in ALDH3A2, which codes for fatty aldehyde dehydrogenase (FALDH) and results in abnormal lipid metabolism. The biochemical abnormalities in SLS are not completely known, and the pathogenic mechanisms leading to symptoms are still unclear. To search for pathways that are perturbed in SLS, we performed untargeted metabolomic screening in 20 SLS subjects along with age- and sex-matched controls. Of 823 identified metabolites in plasma, 121 (14.7%) quantitatively differed in the overall SLS cohort from controls; 77 metabolites were decreased and 44 increased. Pathway analysis pointed to disrupted metabolism of sphingolipids, sterols, bile acids, glycogen, purines and certain amino acids such as tryptophan, aspartate and phenylalanine. Random forest analysis identified a unique metabolomic profile that had a predictive accuracy of 100% for discriminating SLS from controls. These results provide new insight into the abnormal biochemical pathways that likely contribute to disease in SLS and may constitute a biomarker panel for diagnosis and future therapeutic studies.

Choroideremia: molecular mechanisms and therapies

Choroideremia (CHM) is a monogenic X-linked chorioretinal dystrophy affecting the photoreceptors, retinal pigment epithelium (RPE), and choroid; it is caused by mutations involving the CHM gene. CHM is characterized by night blindness in early childhood, progressing to peripheral visual field loss and eventually to complete blindness from middle age. CHM encodes the ubiquitously expressed Rab escort protein 1 (REP1), which is responsible for prenylation of Rab proteins and is essential for intracellular trafficking of vesicles. In this review we explore the role of REP1 in the retina and its newly discovered systemic manifestations, and discuss the therapeutic strategies for tackling this disease, including the outcomes from recent clinical trials.

Small touches to big walks -the impact of rehabilitation on Sjögren-Larsson syndrome: A case report

Sjögren-Larsson syndrome (SLS) is a rare neurocutaneous disorder characterized by the presence of congenital ichthyosis, spasticity, and mental retardation. As with other rare genetic diseases, treatment is mainly symptomatic. Due to the absence of definitive treatment, lifelong follow-up and support of patients are important to improve the quality of life. A 7-year-old female child who was diagnosed as having SLS was referred to the rehabilitation clinic. After 20 sessions of a rehabilitation program, she started walking independently with the additional contribution of ankle-foot orthoses (AFOs). The contribution of the short-term rehabilitation approach and especially the administration of AFOs to the independence level of the patient is emphasized herein.

End-stage crystalline maculopathy with retinal atrophy in Sjögren-Larsson syndrome: a case report and review of the literature

Sjögren-Larsson syndrome (SLS) is a rare, autosomal recessive neurocutaneous disorder. It is caused by the inheritance of sequence variants in the ALDH3A2 gene, which codes for fatty aldehyde dehydrogenase (FALDH). Universal signs of the condition are congenital ichthyosis, spastic paresis of the lower and upper limbs, and reduced intellectual ability. In addition to this clinical triad, patients with SLS experience dry eyes and decreased visual acuity caused by a progressive retinal degeneration. Examination of the retina in patients with SLS often reveals glistening yellow crystal-like deposits surrounding the fovea. This crystalline retinopathy often develops in childhood and is considered pathognomonic for the disease. The metabolic disorder typically shortens lifespan to half that of the unaffected population. However, now that patients with SLS live longer, it becomes increasingly important to understand the natural course of the disease. Our case describes a 58-year-old woman with advanced SLS whose ophthalmic examination illustrates the end-stage of the retinal degeneration. Optical coherence tomography (OCT) and fluorescein angiography confirm the disease is restricted to the neural retina with dramatic thinning of the macula. This case is unique since it is among the most advanced both in terms of chronological age and severity of retinal disease. While the accumulation of fatty aldehydes, alcohols, and other precursor molecules is the probable cause of retinal toxicity, a more complete understanding of the course of retinal degeneration may aid in the development of future treatments. The aim of our presentation of this case is to increase awareness of the disease and to foster interest in therapeutic research which may benefit patients with this rare condition.

Genetic diseases mimicking multiple sclerosis

Multiple sclerosis (MS) is an inflammatory neurodegenerative disorder manifesting as gradual or progressive loss of neurological functions. Most patients present with relapsing-remitting disease courses. Extensive research over recent decades has expounded our insights into the presentations and diagnostic features of MS. Groups of genetic diseases, CADASIL and leukodystrophies, for example, have been frequently misdiagnosed with MS due to some overlapping clinical and radiological features. The delayed identification of these diseases in late adulthood can lead to severe neurological complications. Herein we discuss genetic diseases that have the potential to mimic multiple sclerosis, with highlights on clinical identification and practicing pearls that may aid physicians in recognizing MS-mimics with genetic background in clinical settings.

REP1 deficiency causes systemic dysfunction of lipid metabolism and oxidative stress in choroideremia

Choroideremia (CHM) is an X-linked recessive chorioretinal dystrophy caused by mutations in CHM, encoding for Rab escort protein 1 (REP1). Loss of functional REP1 leads to the accumulation of unprenylated Rab proteins and defective intracellular protein trafficking, the putative cause for photoreceptor, retinal pigment epithelium (RPE), and choroidal degeneration. CHM is ubiquitously expressed, but adequate prenylation is considered to be achieved, outside the retina, through the isoform REP2. Recently, the possibility of systemic features in CHM has been debated; therefore, in this study, whole metabolomic analysis of plasma samples from 25 CHM patients versus age- and sex-matched controls was performed. Results showed plasma alterations in oxidative stress-related metabolites, coupled with alterations in tryptophan metabolism, leading to significantly raised serotonin levels. Lipid metabolism was disrupted with decreased branched fatty acids and acylcarnitines, suggestive of dysfunctional lipid oxidation, as well as imbalances of several sphingolipids and glycerophospholipids. Targeted lipidomics of the chmru848 zebrafish provided further evidence for dysfunction, with the use of fenofibrate over simvastatin circumventing the prenylation pathway to improve the lipid profile and increase survival. This study provides strong evidence for systemic manifestations of CHM and proposes potentially novel pathomechanisms and targets for therapeutic consideration.

Sjögren-Larsson syndrome: Anesthetic considerations and practical recommendations

BACKGROUND

Sjögren-Larsson syndrome is a rare inherited neurocutaneous disorder characterized by congenital ichthyosis, spasticity, intellectual disability, seizures, and ophthalmologic changes. Most individuals with Sjögren-Larsson syndrome live well into adulthood and often require surgical intervention to manage their symptomatology.

AIMS

The aim of this work was to review the clinical aspects of Sjögren-Larsson syndrome, highlight the unique anesthetic considerations associated with this disease, and provide practical recommendations about anesthetic management.

METHODS

A retrospective case review from February 2013 to October 2019 was performed based on subject participation in a Sjögren-Larsson syndrome longitudinal study at the University of Nebraska Medical Center. Anesthetic and surgical records were reviewed for the following data: age, sex, relevant comorbid conditions, anesthetic induction and maintenance agents, intravenous and oral analgesics, muscle relaxants, and anesthetic-related complications.

RESULTS

Fourteen patients with Sjögren-Larsson syndrome undergoing 48 anesthetic events were identified. A variety of anesthetic techniques was utilized. No serious adverse events were encountered. The most common clinical observations were related to the ichthyosis seen in Sjögren-Larsson syndrome, which led to difficulty in adherence of electrocardiogram leads and intravenous catheter dressings.

CONCLUSIONS

We found that anesthesia can be safely administered in patients with Sjögren-Larsson syndrome. Providers should be aware of anesthetic management issues in Sjögren-Larsson syndrome including challenges placing and securing lines and monitors secondary to the ichthyosis.

Macular crystalline inclusions in Sjögren-Larsson syndrome are dynamic structures that undergo remodeling

BACKGROUND

Sjögren-Larsson syndrome (SLS) is a rare genetic neurocutaneous disease caused by mutations in ALDH3A2 that results in deficiency of fatty aldehyde dehydrogenase and accumulation of fatty aldehydes and alcohols. The disease is associated with ichthyosis, spasticity, and intellectual disability. Patients exhibit a characteristic retinopathy with macular crystalline inclusions that first appear in early childhood and increase with age. Once formed, the inclusions are thought to be inert and irreversible. We sought to document how the crystalline inclusions change over time.

MATERIALS AND METHODS

Serial retinal photographs of 4 SLS subjects (9-23 years old) were taken over a period of 1-3 years. Images were compared by visual inspection and analyzed using ImageJ/Fiji software to observe changes.

RESULTS

Visual inspection of retinal photographs of SLS subjects taken over time demonstrated distinctive changes in crystalline inclusions. New inclusions were formed and some established inclusions regressed. These changes were conveniently demonstrated with software-based photographic image analysis.

CONCLUSIONS

We conclude that macular inclusions in SLS are not simply inert deposits, but are dynamic structures that form over time and are subject to remodeling. This conclusion provides new insight into the interplay between the metabolic defect and retinal pathology in SLS, and raises the potential for new therapeutic approaches to reverse some aspects of the maculopathy.

Eye involvement in inherited metabolic disorders

Inherited metabolic disorders are a large group of rare disorders affecting normal biochemical pathways. Many metabolic disorders can present with symptoms affecting the eye, and eye disorders can evolve later in the natural history of an already diagnosed metabolic disorder. The ophthalmic involvement can be very varied affecting any part of the eye, including abnormalities of cornea, lens dislocation and cataracts, retina and the distal optic pathway, and extraocular muscles. Awareness of inherited metabolic disorders is important to facilitate early diagnosis and in some cases instigate early treatment if a patient presents with eye involvement suggestive of a metabolic disorder. Ophthalmological interventions are also an important component of the multisystem holistic approach to treating patients with metabolic disorders.