Hereditary Disorders and Human Mutations of Iron-Sulfur Assembly Genes

Multiple mitochondrial dysfunctions syndrome (MMDS) is a group of autosomal recessive mitochondrial disorders that is associated with deficiencies related to nuclear genes: ISCA2, ISCA1, NFU1, IBA57, and BOLA3. The syndromes are relatively new and recently discovered. Individuals with MMDS have reduced function of energy production stages in mitochondria. The dysfunctions are mostly related to iron-sulfur (Fe-S) clustering system (ISC) and its biogenesis. The signs and symptoms of the patients may begin early in life, and can be quite severe leading to death more or less during infancy. Affected individuals have various symptoms including brain dysfunction (encephalopathy), hypotonia, seizures, delayed developmental milestones, and cognition and psychomotor impairments. These individuals often have difficulty growing and gaining weight at the expected rate. Diagnosis of the disease can be challenging as in the case with most of the mitochondrial disorders. However, since the genetic causes of the MMDS are known, a laboratory test focusing on the causative genes will be helpful to determine the pathogenic mutations. This in turn would facilitate reducing the number of the diseases through carrier testing and genetic counseling and utilization of preimplantation genetic diagnosis in populations, especially those that display high rate of consanguinity, which are prone to have such autosomal recessive disorders

Guidelines for acute management of hyperammonemia in the Middle East region

BACKGROUND: Hyperammonemia is a life-threatening event that can occur at any age. If treated, the early symptoms in all age groups could be reversible. If untreated, hyperammonemia could be toxic and cause irreversible brain damage to the developing brain. OBJECTIVE: There are major challenges that worsen the outcome of hyperammonemic individuals in the Middle East. These include: lack of awareness among emergency department physicians about proper management of hyperammonemia, strained communication between physicians at primary, secondary, and tertiary hospitals, and shortage of the medications used in the acute management of hyperammonemia. Therefore, the urge to develop regional guidelines is extremely obvious. METHOD: We searched PubMed and Embase databases to include published materials from 2011 to 2014 that were not covered by the European guidelines, which was published in 2012. We followed the process of a Delphi conference and involved one preliminary meeting and two follow-up meetings with email exchanges between the Middle East Hyperammonemia and Urea Cycle Disorders Scientific Group regarding each draft of the manuscript. RESULTS AND DISCUSSION: We have developed consensus guidelines based on the highest available level of evidence. The aim of these guidelines is to homogenize and harmonize the treatment protocols used for patients with acute hyperammonemia, and to provide a resource to not only metabolic physicians, but also physicians who may come in contact with individuals with acute hyperammonemia. CONCLUSION: These suggested guidelines aim to ease the challenges faced by physicians dealing with acute hyperammonemia in the region. In addition, guidelines have demonstrated useful collaboration between experts in the region, and provides information that will hopefully improve the outcomes of patients with acute hyperammonemia

Guidelines for acute management of hyperammonemia in the Middle East region

BACKGROUND: Hyperammonemia is a life-threatening event that can occur at any age. If treated, the early symptoms in all age groups could be reversible. If untreated, hyperammonemia could be toxic and cause irreversible brain damage to the developing brain. OBJECTIVE: There are major challenges that worsen the outcome of hyperammonemic individuals in the Middle East. These include: lack of awareness among emergency department physicians about proper management of hyperammonemia, strained communication between physicians at primary, secondary, and tertiary hospitals, and shortage of the medications used in the acute management of hyperammonemia. Therefore, the urge to develop regional guidelines is extremely obvious. METHOD: We searched PubMed and Embase databases to include published materials from 2011 to 2014 that were not covered by the European guidelines, which was published in 2012. We followed the process of a Delphi conference and involved one preliminary meeting and two follow-up meetings with email exchanges between the Middle East Hyperammonemia and Urea Cycle Disorders Scientific Group regarding each draft of the manuscript. RESULTS AND DISCUSSION: We have developed consensus guidelines based on the highest available level of evidence. The aim of these guidelines is to homogenize and harmonize the treatment protocols used for patients with acute hyperammonemia, and to provide a resource to not only metabolic physicians, but also physicians who may come in contact with individuals with acute hyperammonemia. CONCLUSION: These suggested guidelines aim to ease the challenges faced by physicians dealing with acute hyperammonemia in the region. In addition, guidelines have demonstrated useful collaboration between experts in the region, and provides information that will hopefully improve the outcomes of patients with acute hyperammonemia

Biallelic loss of LDB3 leads to a lethal pediatric dilated cardiomyopathy

Autosomal dominant variants in LDB3 (also known as ZASP), encoding the PDZ-LIM domain-binding factor, have been linked to a late onset phenotype of cardiomyopathy and myofibrillar myopathy in humans. However, despite knockout mice displaying a much more severe phenotype with premature death, bi-allelic variants in LDB3 have not yet been reported. Here we identify biallelic loss-of-function variants in five unrelated cardiomyopathy families by next-generation sequencing. In the first family, we identified compound heterozygous LOF variants in LDB3 in a fetus with bilateral talipes and mild left cardiac ventricular enlargement. Ultra-structural examination revealed highly irregular Z-disc formation, and RNA analysis demonstrated little/no expression of LDB3 protein with a functional C-terminal LIM domain in muscle tissue from the affected fetus. In a second family, a homozygous LDB3 nonsense variant was identified in a young girl with severe early-onset dilated cardiomyopathy with left ventricular non-compaction; the same homozygous nonsense variant was identified in a third unrelated female infant with dilated cardiomyopathy. We further identified homozygous LDB3 frameshift variants in two unrelated probands diagnosed with cardiomegaly and severely reduced left ventricular ejection fraction. Our findings demonstrate that recessive LDB3 variants can lead to an early-onset severe human phenotype of cardiomyopathy and myopathy, reminiscent of the knockout mouse phenotype, and supporting a loss of function mechanism

Biallelic variants in FLII cause pediatric cardiomyopathy by disrupting cardiomyocyte cell adhesion and myofibril organization

Pediatric cardiomyopathy (CM) represents a group of rare, severe disorders that affect the myocardium. To date, the etiology and mechanisms underlying pediatric CM are incompletely understood, hampering accurate diagnosis and individualized therapy development. Here, we identified biallelic variants in the highly conserved flightless-I (FLII) gene in 3 families with idiopathic, early-onset dilated CM. We demonstrated that patient-specific FLII variants, when brought into the zebrafish genome using CRISPR/Cas9 genome editing, resulted in the manifestation of key aspects of morphological and functional abnormalities of the heart, as observed in our patients. Importantly, using these genetic animal models, complemented with in-depth loss-of-function studies, we provided insights into the function of Flii during ventricular chamber morphogenesis in vivo, including myofibril organization and cardiomyocyte cell adhesion, as well as trabeculation. In addition, we identified Flii function to be important for the regulation of Notch and Hippo signaling, crucial pathways associated with cardiac morphogenesis and function. Taken together, our data provide experimental evidence for a role for FLII in the pathogenesis of pediatric CM and report biallelic variants as a genetic cause of pediatric CM.</p

Lunapark deficiency leads to an autosomal recessive neurodevelopmental phenotype with a degenerative course, epilepsy and distinct brain anomalies

LNPK encodes a conserved membrane protein that stabilizes the junctions of the tubular endoplasmic reticulum network playing crucial roles in diverse biological functions. Recently, homozygous variants in LNPK were shown to cause a neurodevelopmental disorder (OMIM#618090) in four patients displaying developmental delay, epilepsy and nonspecific brain malformations including corpus callosum hypoplasia and variable impairment of cerebellum. We sought to delineate the molecular and phenotypic spectrum of LNPK-related disorder. Exome or genome sequencing was carried out in 11 families. Thorough clinical and neuroradiological evaluation was performed for all the affected individuals, including review of previously reported patients. We identified 12 distinct homozygous loss-of-function variants in 16 individuals presenting with moderate to profound developmental delay, cognitive impairment, regression, refractory epilepsy and a recognizable neuroimaging pattern consisting of corpus callosum hypoplasia and signal alterations of the forceps minor ('ear-of-the-lynx' sign), variably associated with substantia nigra signal alterations, mild brain atrophy, short midbrain and cerebellar hypoplasia/atrophy. In summary, we define the core phenotype of LNPK-related disorder and expand the list of neurological disorders presenting with the 'ear-of-the-lynx' sign suggesting a possible common underlying mechanism related to endoplasmic reticulum-phagy dysfunction

Ethical solicitude in medical genetics as perceived from a genetic counselor&apos;s perspective in the tribal-based community of Saudi Arabia

Background: The genetics domain is witnessing great advances in diagnosing and predicting genetic diseases. In a clinical setting, autosomal recessive genetic disorders are frequently observed as a result of the high rate of consanguinity. The advances in genomic technologies and methods in recent years have facilitated new tools for gene discovery in humans. There is a debate over the ethical dilemmas and challenges behind providing families with the genetic test results and incidental findings. Thus, this vast source of information can have a multitude of ethical, social, legal, and political implications. Objectives: In this study, we aimed to study how families of affected children respond when they receive incidental findings. Also, we aimed to identify how healthcare professionals descriptively abide by their role and the information-sharing procedures. Methods: This study was a qualitative study conducted at King Faisal Specialist Hospital and Research Centre in Riyadh. It included a total of 14 participants and a total of 14 healthcare providers. Results and conclusion: Six strong themes emerged in this study. This study explored the experiences of parents of children affected with genetic diseases and the experiences of healthcare providers attending these families; their observations and the ethical challenges they faced during their practice. [JBCGenetics 2021; 4(2.000): 100-111

A case report of a first pregnant woman with late-onset multiple acyl-CoA dehydrogenase deficiency in Saudi Arabia

Background: Multiple acyl-CoA dehydrogenase deficiency (MADD), also known as glutaric aciduria II, is a rare autosomal recessively inherited disorder of inborn error of metabolism. It can mainly be presented in three phenotypes: severe neonatal onset with a dysmorphic feature, neonatal-onset without dysmorphic features, and less severe mild late-onset phenotype. Case presentation: A 34-year-old Saudi female previously healthy, Para 4, with severe metabolic acidosis, rhabdomyolysis intrapartum was presented to us. Her previous pregnancy history and deliveries were unremarkable; she has three healthy sons. Since the beginning of this pregnancy, she complained of fatigability and muscle weakness which was progressive with time. At 36 weeks of gestation, she was presented to the emergency room with labor pain. She deteriorated rapidly with significant drowsiness. Her arterial blood gas showed severe metabolic acidosis with a high anion gap and normal lactate. She was intubated and underwent emergency cesarean delivery under general anesthesia. After the operation, she was sent to the intensive care unit. She passed away after a few days. A molecular test confirmed the diagnosis of MADD. Conclusion: First, late-onset MADD is a rare, underdiagnosed disease in adults. Second, the biochemical diagnosis of late-onset MADD is challenging as it mimics medium chain acyl CoA dehydrogenase deficiency which makes the molecular diagnosis essential for diagnosis. Third, for any unexplained myopathy, cardiac dysfunction, encephalopathy, or metabolic acidosis, metabolic disorders must be considered as early consultation with metabolic service. [JBCGenetics 2022; 5(1.000): 20-24

Rubinstein-Taybi syndrome in a Saudi boy with distinct features and variants in both the CREBBP and EP300 genes: a case report

Abstract Background Rubinstein-Taybi syndrome (RSTS) Type 1 (OMIM 180849) is characterized by three main features: intellectual disability; broad and frequently angulated thumbs and halluces; and characteristic facial dysmorphism. Case presentation We report on a Saudi boy with RSTS Type 1 and the following distinct features: a midline notch of the upper lip, a bifid tip of the tongue, a midline groove of the lower lip, plump fingers with broad / flat fingertips, and brachydactyly. The child was found to be heterozygous in the CREBBP gene for a sequence variant designated c.4963del, which is predicted to result in premature protein termination p.Leu1655Cysfs*89. The child and his father were also found to be heterozygous in the EP300 gene for a sequence variant designated c.586A > G, which is predicted to result in the amino-acid substitution p.Ile196Val. Conclusion Our report expands the clinical spectrum of RSTS to include several distinct facial and limb features. The variant of the CREBBP gene is known to be causative of RSTS Type 1. The variant in the EP300 gene is benign since the father carried the same variant and exhibited no abnormalities. However, functional studies are required to investigate if this benign EP300 variant influences the phenotype in the presence of disease-causing CREBBP gene mutations