A de novo ANK1 mutation associated to hereditary spherocytosis: a case report

Gastrulation-stage gene expression in Nipbl +/- mouse embryos foreshadows the development of syndromic birth defects

In animal models, Nipbl-deficiency phenocopies gene expression changes and birth defects seen in Cornelia de Lange Syndrome (CdLS), the most common cause of which is Nipbl-haploinsufficiency. Previous studies in Nipbl+/- mice suggested that heart development is abnormal as soon as cardiogenic tissue is formed. To investigate this, we performed single-cell RNA-sequencing on wildtype (WT) and Nipbl+/- mouse embryos at gastrulation and early cardiac crescent stages. Nipbl+/- embryos had fewer mesoderm cells than WT and altered proportions of mesodermal cell subpopulations. These findings were associated with underexpression of genes implicated in driving specific mesodermal lineages. In addition, Nanog was found to be overexpressed in all germ layers, and many gene expression changes observed in Nipbl+/- embryos could be attributed to Nanog overexpression. These findings establish a link between Nipbl-deficiency, Nanog overexpression, and gene expression dysregulation/lineage misallocation, which ultimately manifest as birth defects in Nipbl+/- animals and CdLS.

Teaser

Gene expression changes during gastrulation of Nipbl-deficient mice shed light on early origins of structural birth defects.

Case of Congenital Hemolytic Anemia with ATP11C and ANK1 Variants

A male infant of Han descent, with a G1P1 mother and gestational age of 40+4 weeks, was born via cesarean section owing to his mother having pregnancy complications, including premature rupture of membranes, chorioamnionitis, and gestational diabetes. On the first day after birth, routine blood examination showed that his total red blood cells count was 2.32 × 1012/L, hemoglobin count was 77 g/L, and C-reactive protein count was 48.99 mg/L. After receiving an anti-infection treatment for 10 days and two blood transfusions (100 mL in total), he was discharged from a neonatal intensive care unit (NICU). Accessory examinations showed that reticulocytes in the peripheral blood were significantly increased, the morphology of red blood cells was normal, and all hemolysis-related examinations were normal; bone marrow examinations showed that the proliferation of the red blood cell system was low and serum ferritin and vitamin B12 levels were elevated. Because of the unexplained hemolysis, a whole-exome sequencing examination was performed. The results showed a hemizygous variant of the ATP11C gene (c.3136a>t/p ile 1046phe) and a frame-shift variant of the ANK1 gene (c.937del/pala313 leufs*19). After a six-month follow-up, the serum ferritin and vitamin B12 levels had gradually decreased to normal levels, and hemoglobin and reticulocyte values were 97 g/L and 7.17%, respectively, in the peripheral blood. No splenomegaly was found in physical examination.

Clinical manifestations of 17 Chinese children with hereditary spherocytosis caused by novel mutations of the ANK1 gene and phenotypic analysis

Background: Hereditary spherocytosis (HS) is an autosomal dominant (AD) and autosomal recessive (AR) disorder that is mostly caused by mutations of the erythrocyte membrane-related gene ANK1. Methods: Clinical and genetic testing data of 17 HS children with ANK1 gene mutations were retrospectively collected. Clinical manifestations and phenotypic analysis of HS were summarized based on our experience and literature review. Results: A total of 17 mutations of the ANK1 gene were identified from 17 probands (12 sporadic cases and five familial cases), including 15 novel mutations and two previously reported ones. Among the 15 novel variants of ANK1, there were four non-sense mutations, four frameshift mutations, three splicing mutations, three missense mutations and one in-frame deletion of three amino acids. In the present study, HS patients with mutations in membrane binding domains had significantly lower hemoglobin (Hb) levels and higher total bilirubin (T-Bil) levels than those with mutations in regulatory domains. After reviewing and analyzing all available published reports of Chinese HS patients carrying ANK1 mutations in PubMed and Chinese journals, there were no significant differences in Hb, Ret and T-Bil between different mutation types or mutation regions. Conclusion: Mutations of the ANK1 can be inherited or de novo. Clinical manifestations of HS in children caused by ANK1 mutations are similar to those of other types of hemolytic anemia. Our report expands the mutation spectrum of HS, thus providing references for clinical management and genetic counseling of HS.

De novo variations of ANK1 gene caused hereditary spherocytosis in two Chinese children by affecting pre-mRNA splicing

BACKGROUND AND AIMS

Hereditary spherocytosis (HS) is one of the most common hereditary haemolytic disorders. Here, two unrelated families with the probands displaying typical manifestations of HS were enrolled. Our study aimed to characterize the effect of two novel variants in HS patients on gene splicing to help minimize the rate of misdiagnosis of HS and enhance clinicians' understanding of the disease.

PARTICIPANTS AND METHODS

A retrospective review was conducted. Peripheral blood samples were collected from all the family members, and genomic DNA was extracted for genetic diagnostics. First, high-throughput sequencing technology was used for the preliminary screening of candidate causative variants. Thereafter, the variants were verified via Sanger sequencing. Furthermore, a pathogenicity analysis of the detected variants was performed including in silico prediction and in vitro experiments. We constructed matched wild-type and mutant-type minigene plasmid of ANK1 based on HEK293T cells to address the effects of variants on mRNA splicing.

RESULTS

The c.1305 + 2 T > A (family1) and c.1305 + 2del (family2) variants were detected in the ANK1 gene. These two de novo mutations described by us which have not been reported prior to this study. Moreover, the validation results of splicing reporter systems revealed that the intronic mutations resulted in abnormal pre-mRNA splicing. Specifically, the minigene plasmid expressing the c.1305 + 2 T > A variant transcribed the two aberrant transcripts: r.1305_1306ins1305 + 1_1305 + 229 and r.1305_1306ins1305 + 1_1305 + 552. The minigene plasmid expressing c.1305 + 2del transcribed the two aberrant transcripts: r.1305_1306ins1305 + 1_1305 + 228 and r.1305_1306ins1305 + 1_1305 + 551.

CONCLUSION

The two de novo variants identified in the ANK1 gene were the genetic etiology of the probands with HS in our study. Our findings further enrich the HS genotype database and provide a basis for genetic counselling and molecular diagnosis.

Severe hyperbilirubinemia in a neonate with hereditary spherocytosis due to a de novo ankyrin mutation: A case report

BACKGROUND

Hereditary spherocytosis (HS) is a common type of hemolytic anemia caused by a red cell membrane disorder. HS type 1 (HS1) is mostly caused by mutations in ankyrin (ANK1). Newborns with HS1 usually only exhibit anemia and mild jaundice. We herein report a case of HS1 and discuss its clinical characteristics.

CASE SUMMARY

A 2-d-old male full-term newborn was admitted to our hospital with severe, intractable neonatal jaundice. Laboratory investigations showed hemolytic anemia and hyperbilirubinemia and excluded immune-mediated hemolysis. The patient underwent two exchange transfusions and one plasmapheresis resulting in significantly reduced serum bilirubin. Hematologic analyses and genomic DNA sequencing studies were performed. The trio clinical exome sequencing revealed a de novo null heterozygous mutation in the patient's ANK1 gene: c.841C > T(p.Arg281Ter). This mutation results in the premature termination of the ANK1 protein.

CONCLUSION

Our case demonstrates that genetic analysis can be an essential method for diagnosing HS when a newborn has severe hyperbilirubinemia.

The Successful Use of an Exchange Transfusion in a Child with Hereditary Spherocytosis Undergoing Congenital Cardiac Surgery

Little is reported in the literature regarding hereditary spherocytosis (HS) and cardiopulmonary bypass (CPB). We present a case of a 19-month-old girl child who was referred for an atrioventricular septal defect (AVSD) and HS. The patient underwent surgical repair, and an exchange transfusion was performed at the initiation of CPB. No significant hemolysis or events attributed to HS were observed during or after CPB. The surgical repair of an AVSD in a pediatric patient with HS and total volume exchange transfusion is herein reported.