A de novo interstitial deletion of 8p11.2 including ANK1 identified in a patient with spherocytosis, psychomotor developmental delay, and distinctive facial features

Ankyrin-R Links Kv3.3 to the Spectrin Cytoskeleton and Is Required for Purkinje Neuron Survival

Ankyrin scaffolding proteins are critical for membrane domain organization and protein stabilization in many different cell types including neurons. In the cerebellum, Ankyrin-R (AnkR) is highly enriched in Purkinje neurons, granule cells, and in the cerebellar nuclei (CN). Using male and female mice with a floxed allele for Ank1 in combination with Nestin-Cre and Pcp2-Cre mice, we found that ablation of AnkR from Purkinje neurons caused ataxia, regional and progressive neurodegeneration, and altered cerebellar output. We show that AnkR interacts with the cytoskeletal protein β3 spectrin and the potassium channel Kv3.3. Loss of AnkR reduced somatic membrane levels of β3 spectrin and Kv3.3 in Purkinje neurons. Thus, AnkR links Kv3.3 channels to the β3 spectrin-based cytoskeleton. Our results may help explain why mutations in β3 spectrin and Kv3.3 both cause spinocerebellar ataxia.SIGNIFICANCE STATEMENT Ankyrin scaffolding proteins localize and stabilize ion channels in the membrane by linking them to the spectrin-based cytoskeleton. Here, we show that Ankyrin-R (AnkR) links Kv3.3 K+ channels to the β3 spectrin-based cytoskeleton in Purkinje neurons. Loss of AnkR causes Purkinje neuron degeneration, altered cerebellar physiology, and ataxia, which is consistent with mutations in Kv3.3 and β3 spectrin causing spinocerebellar ataxia.

Early-Onset Diabetes Mellitus in Chromosome 8p11.2 Deletion Syndrome Combined With Becker Muscular Dystrophy - A Case Report

BACKGROUND

Chromosome 8p11.2 includes several key genes in development such as the FGFR1, ANK1, KAT6A, and SLC20A2 genes. Deletion of this fragment causes a contiguous gene syndrome. Currently, few cases of interstitial deletion of whole 8p11.2 have been reported. We report a rare case of 8p11.2 deletion syndrome with the unique phenotypes, presenting with early-onset diabetes.

CASE DESCRIPTION

A 20-year-old man with a 1-year history of diabetes mellitus was admitted to the Endocrinology Clinic. Physical examination revealed the dysmorphic facial features, and broad and foreshortened halluces. Laboratory examination indicated spherocytosis anemia, and hypogonadotropic hypogonadism. Bone mineral density analysis showed decreased bone density in the lumbar vertebrae. Brain CT showed calcification. Whole-exome sequencing revealed a 7.05-Mb deletion in 8p11 containing 43 OMIM genes, and a large in-frame deletion of exons 48-55 in the DMD gene. Metformin was given to the patient after which his blood glucose was well controlled. HCG was injected subcutaneously and was supplemented with calcium and vitamin D, which led to an improvement in the patient's quality of life.

CONCLUSION

We report a rare case of 8p11.2 deletion syndrome with unique phenotypes, and early-onset diabetes. It is challenging for endocrinologists to simultaneously reconcile a combination of these diseases across multiple disciplines. We discussed the influencing factors of early-onset diabetes in this patient and speculated that it was caused by complex interactions of known and unknown genetic backgrounds and environmental factors.

Ankyrin-R regulates fast-spiking interneuron excitability through perineuronal nets and Kv3.1b K+ channels

Neuronal ankyrins cluster and link membrane proteins to the actin and spectrin-based cytoskeleton. Among the three vertebrate ankyrins, little is known about neuronal Ankyrin-R (AnkR). We report AnkR is highly enriched in Pv⁺ fast-spiking interneurons in mouse and human. We identify AnkR-associated protein complexes including cytoskeletal proteins, cell adhesion molecules (CAMs), and perineuronal nets (PNNs). We show that loss of AnkR from forebrain interneurons reduces and disrupts PNNs, decreases anxiety-like behaviors, and changes the intrinsic excitability and firing properties of Pv⁺ fast-spiking interneurons. These changes are accompanied by a dramatic reduction in Kv3.1b K⁺ channels. We identify a novel AnkR-binding motif in Kv3.1b, and show that AnkR is both necessary and sufficient for Kv3.1b membrane localization in interneurons and at nodes of Ranvier. Thus, AnkR regulates Pv⁺ fast-spiking interneuron function by organizing ion channels, CAMs, and PNNs, and linking these to the underlying β1 spectrin-based cytoskeleton.

Ankyrins and neurological disease

Ankyrins are scaffolding proteins widely expressed throughout the nervous system. Ankyrins recruit diverse membrane proteins, including ion channels and cell adhesion molecules, into specialized subcellular membrane domains. These domains are stabilized by ankyrins interacting with the spectrin cytoskeleton. Ankyrin genes are highly associated with a number of neurological disorders, including Alzheimer's disease, schizophrenia, autism spectrum disorders, and bipolar disorder. Here, we discuss ankyrin function and their role in neurological disease. We propose mutations in ankyrins contribute to disease through two primary mechanisms: 1) altered neuronal excitability by disrupting ion channel clustering at key excitable domains, and 2) altered neuronal connectivity via impaired stabilization of membrane proteins.

Autism and severe clinical phenotype in a patient with 8p21.2p11.21 deletion: Case report and literature review

Interstitial 8p deletions were previously described, in literature and databases, in approximately 30 patients with neurodevelopmental disorders. We report on a novel patient with a 8p21.2p11.21 deletion presenting a clinical phenotype that includes severe intellectual disability, microcephaly, epilepsy, and autism, the latter having been rarely associated with this genetic defect.

Global retardation and hereditary spherocytosis associated with a novel deletion of chromosome 8p11.21 encompassing KAT6A and ANK1

The loss of heterozygosity localized at chromosome segment 8p11.2 causes a contiguous gene syndrome, which mostly combined phenotype of Kallmann syndrome and hereditary spherocytosis. It has been documented that this combined phenotype is in association with both the deletion of the fibroblast growth factor receptor 1 (FGFR1) and ankyrin 1 (ANK1) genes. Here, we described a 6-year-old girl with microcephaly, global developmental delay, mental retardation, and hereditary spherocytosis, associated with a heterozygous pathogenic microdeletion of 1.9 Mb size at 8p11.21. Molecular analysis confirmed that the identified microdeletion contained two OMIM (Online Mendelian Inheritance in Man)genes, including ANK1 and lysine acetyltransferase 6 A (KAT6A), but not FGFR1. Therefore, the simultaneous occurrence of mild developmental delay and distinctive facial in this patient was associated with the pathogenic variation of the KAT6A.

Pediatric Idiopathic Basal Ganglia Calcification and Spherocytosis With Chromosome 8p11 Deletion

Idiopathic basal ganglia calcification (IBGC), also known as Fahr disease, is a rare neurodegenerative disorder characterized by the accumulation of extensive parenchymal and vascular calcifications in the basal ganglia, with variable calcifications elsewhere in the brain. Typically, IBGC presents with neurologic and psychiatric symptoms in middle-aged adults. Recent genetic studies have identified alterations in 4 genes causing IBGC, including alterations in SLC20A2 on chromosome 8p11.2. Currently, there are no clinical descriptions of patients with IBGC occurring within the context of a complex genetic syndrome. Here, we present a case of pediatric 8p11 deletion with IBGC, hereditary spherocytosis, vitreoretinopathy, and focal cortical dysplasia. We review multiple cases of IBGC with pediatric onset due to SLC20A2 deletion in the literature, and raise the consideration of IBGC in the evaluation of pediatric patients with 8p11.2 deletion syndromes.

Targeted next-generation sequencing identified a novel ANK1 mutation associated with hereditary spherocytosis in a Chinese family

Objectives: Hereditary spherocytosis (HS) represents a group of congenital diseases characterized by sphere-shaped erythrocytes on peripheral blood smears. The typical clinical manifestations of HS include haemolysis, jaundice, splenomegaly, and gallstones. Ankyrin1, encoded by the ANK1 gene, is the predominant protein in red blood cells. Defects in ankyrin1 lead to a decrease in erythrocyte surface area, a spherical shape of erythrocytes and, in particular, loss of membrane elasticity and mechanical stability. The purpose of this study was to investigate a Chinese family with HS to determine the causative gene mutation and explore the genotype-phenotype correlation. Methods: A 4-year-old boy was diagnosed with HS based on typical clinical features. In addition, his father had a high possibility of HS. Targeted next-generation sequencing (NGS) followed by Sanger sequencing was performed in the proband and his parents. Results: One mutation in the ANK1 gene was recognized. c1801-1G > C in exon 17, which leads to splicing defects, was detected. To confirm the c1801-1G > C variant, samples from the proband and his parents were analysed by Sanger sequencing, and Sanger verification showed that this mutation was inherited from the father. Conclusion: The present study confirmed that a novel mutation in ANK1 may be causative of HS, which plays an important role in expanding the mutational spectrum of ANK1 mutations. This may contribute to accurate genetic counselling. And it is helpful for understanding the correlation of the genotype and phenotype.

Advances in understanding the pathogenesis of red cell membrane disorders

Hereditary erythrocyte membrane disorders are caused by mutations in genes encoding various transmembrane or cytoskeletal proteins of red blood cells. The main consequences of these genetic alterations are decreased cell deformability and shortened erythrocyte survival. Red blood cell membrane defects encompass a heterogeneous group of haemolytic anaemias caused by either (i) altered membrane structural organisation (hereditary spherocytosis, hereditary elliptocytosis, hereditary pyropoikilocytosis and Southeast Asian ovalocytosis) or (ii) altered membrane transport function (overhydrated hereditary stomatocytosis, dehydrated hereditary stomatocytosis or xerocytosis, familial pseudohyperkalaemia and cryohydrocytosis). Herein we provide a comprehensive review of the recent literature on the molecular genetics of erythrocyte membrane defects and their reported clinical consequences. We also describe the effect of low-expression genetic variants on the high inter- and intra-familial phenotype variability of erythrocyte structural defects.

Molecular Genetic Mechanisms of Hereditary Spherocytosis: Current Perspectives

With the widespread use of genetic diagnostic technologies, many novel mutations have been identified in hereditary spherocytosis (HS)-related genes, including SPTA1, SPTB, ANK1, SLC4A1, and EPB42. However, mutations in HS-related genes are dispersed and nonspecific in the diagnosis of some HS patients, indicating significant heterogeneity in the molecular deficiency of HS. It is necessary to provide the molecular and genetic characteristics of these 5 genes for clinicians to examine HS. Here, we reviewed the recent proposed molecular genetic mechanisms of HS.

An ANK1 IVS3-2A>C mutation causes exon 4 skipping in two patients from a Chinese family with hereditary spherocytosis

Hereditary spherocytosis (HS) is a congenital hemolytic anemia that affects the cell membrane of red blood cells and is characterized by the presence of spherical-shaped erythrocytes in the peripheral blood film. The clinical manifestation of HS ranges from asymptomatic to severe cases that require transfusion during early childhood. HS is caused by mutations in red blood cell membrane protein encoding genes, including ANK1, EPB42, SLC4A1, SPTA1, and SPTB. Mutations of the ANK1 gene account for 75% of all HS cases, and these particular mutations are typically inherited in an autosomal dominant manner. In this study, heterozygous an ANK1 IVS3-2A>C mutation was identified in a 7-year-old girl with Coombs-negative and severe hemolytic jaundice using targeted next-generation sequencing (NGS) and Sanger sequencing. Spherocytes were observed in a peripheral smear. Osmotic fragility was increased, and glucose-6-phosphate dehydrogenase (G6PD) activity was normal. A genetic mutation screen for α- and β-thalassemia was negative. Autoimmune antibody tests were negative. Both the girl and her affected father received a splenectomy. Patient-derived peripheral blood mononuclear cells showed skipping of exon 4 in the mRNA, which confirmed the splicing mutation effect of the ANK1 IVS3-2A>C mutation. Moreover, the anemia was ameliorated after splenectomy. Our results demonstrate that the ANK1 IVS3-2A>C mutation may lead to exon 4 skipping of the ANK1 gene and cause HS.

miR-486 functions as a tumor suppressor in esophageal cancer by targeting CDK4/BCAS2

Esophageal cancer is a common tumor for which morbidity and mortality are high worldwide. We aimed to study alterations in miR-486 expression in esophageal cancers, and the effect miR-486 on esophageal cancer cell function and behavior. We collected esophageal cancer tissues/corresponding normal tissues from 20 patients and utilized three esophageal cancer cell lines and normal esophageal epithelial cells, and the expression of miR-486, CDK4 and BCAS2 was detected by qRT-PCR. Western blotting was used to detect the expression of CDK4 and BCAS2 protein. Then, we overexpressed miR-486 in esophageal cancer cell line EC9706. A series of cell functional analyses, including cell growth, cell cycle, apoptosis, migration and invasion were performed in esophageal cancer cells using colony formation assay, flow cytometry, Transwell and scratch assays, respectively. Dual-Luciferase reporter gene assay was used to detect the target genes of miR-486. We found that the expression of miR-486 in esophageal cancer tissues and cell lines was significantly lower than that in the normal tissues and normal esophageal epithelial cell line. Overexpression of miR-486 significantly inhibited the colony formation ability, induced G0/G1 phase arrest and apoptosis and suppressed cell migration and invasion in the EC9706 cells. Using bioinformatics and luciferase reporter assay, we identified that CDK4 and BCAS2 may be target genes of miR-486 and levels of CDK4 and BCAS2 were both significantly higher in the esophageal cancer tissues and cell lines than levels in the normal tissues and cells. Furthermore, knockdown of CDK4/BCAS2 coincided with the suppressive effects of miR-486 in esophageal cancer cells. Expression of apoptotic signaling molecules p21 and caspase-3 was upregulated in the CDK4/BCAS2-knockdown groups. These results suggest that miR-486 may suppress tumor cell growth and metastasis in esophageal cancer by targeting CDK4/BCAS2. The newly identified miR-486/CDK4/BCAS2 pathway provides further insight into the development and progression of esophageal cancer, which is of great significance to the early diagnosis and detection of esophageal cancer.

New insights on hereditary erythrocyte membrane defects

After the first proposed model of the red blood cell membrane skeleton 36 years ago, several additional proteins have been discovered during the intervening years, and their relationship with the pathogenesis of the related disorders have been somewhat defined. The knowledge of erythrocyte membrane structure is important because it represents the model for spectrin-based membrane skeletons in all cells and because defects in its structure underlie multiple hemolytic anemias. This review summarizes the main features of erythrocyte membrane disorders, dividing them into structural and altered permeability defects, focusing particularly on the most recent advances. New proteins involved in alterations of the red blood cell membrane permeability were recently described. The mechanoreceptor PIEZO1 is the largest ion channel identified to date, the fundamental regulator of erythrocyte volume homeostasis. Missense, gain-of-function mutations in the PIEZO1 gene have been identified in several families as causative of dehydrated hereditary stomatocytosis or xerocytosis. Similarly, the KCNN4 gene, codifying the so called Gardos channel, has been recently identified as a second causative gene of hereditary xerocytosis. Finally, ABCB6 missense mutations were identified in different pedigrees of familial pseudohyperkalemia. New genomic technologies have improved the quality and reduced the time of diagnosis of these diseases. Moreover, they are essential for the identification of the new causative genes. However, many questions remain to solve, and are currently objects of intensive studies.

Genetic diagnosis of idiopathic hypogonadotrophic hypogonadism: a new point mutation in the KAL2 gene

Kallmann Syndrome (KS) is a genetic disease of embryonic development which is characterized by the association of hypogonadotropic hypogonadism (HH) due to a deficit of the gonadotropin-releasing hormone (GnRH) and a hypo/anosmia (including a hypoplasia of the nasal sulcus and agenesis of the olfactory bulbs). Even though it is a genotypically and phenotypically heterogeneous clinical disease, there are some key genes related to KS (KAL1, FGFR1 (KAL2), GNRHR, KISSR1 (GPR54), GNRH1, NELF and PROK2). The aim of this study was to present a case report of a genetic diagnosis of KS linked to the presence of mutations in the FGFR1 (fibroblast growth factor receptor 1, also known as KAL2) gene. This diagnosis was made in a 44-year old female affected by a hypogonadism for which she had received intermittent treatment until she was 30 years old based on the patient's own decision. The molecular analysis of FGFR1 identified the mutation c. 246_247delAG (p.T82Xfs110) in heterozygosis on exon 3 of the KAL2 gene. This is the first report of this mutation related to idiopathic hypogonadotrophic hypogonadism (IHH).