Ion channels provide the basis for the nervous system’s intrinsic electrical activity. Neuronal excitability is a characteristic property of neurons and is critical for all functions of the nervous system. Glia cells fulfill essential supportive roles, but unlike neurons, they also retain the ability to divide. This can lead to uncontrolled growth and the formation of gliomas. Ion channels are involved in the unique biology of gliomas pertaining to peritumoral pathology and seizures, diffuse invasion, and treatment resistance. The emerging picture shows ion channels in the brain at the crossroads of neurophysiology and fundamental pathophysiological processes of specific cancer behaviors as reflected by uncontrolled proliferation, infiltration, resistance to apoptosis, metabolism, and angiogenesis. Ion channels are highly druggable, making them an enticing therapeutic target. Targeting ion channels in difficult-to-treat brain tumors such as gliomas requires an understanding of their extremely heterogenous tumor microenvironment and highly diverse molecular profiles, both representing major causes of recurrence and treatment resistance. In this review, we survey the current knowledge on ion channels with oncogenic behavior within the heterogeneous group of gliomas, review ion channel gene expression as genomic biomarkers for glioma prognosis and provide an update on therapeutic perspectives for repurposed and novel ion channel inhibitors and electrotherapy.
Krüppel-type zinc finger genes (ZNF) constitute a large yet relatively poorly characterized gene family. ZNF genes encode proteins that recognize specific DNA motifs in gene promotors. They act as transcriptional co-activators or -repressors via interaction with chromatin remodeling proteins and other transcription factors. Only few ZNF genes are currently linked to human disorders and identification of ZNF gene-associated human diseases may help understand their function. Here we provide genetic, statistical, and clinical evidence to support association of ZNF148 with a new intellectual disability (ID) syndrome disorder. Routine diagnostic exome sequencing data were obtained from 2172 patients with ID and/or multiple congenital anomalies. In a cohort of 2172 patient–parent trios referred for routine diagnostic whole exome sequencing for ID and/or multiple congenital anomalies (MCA) in the period 2012–2016, four patients were identified who carried de novo heterozygous nonsense or frameshift mutations in the ZNF148 gene. This was the only ZNF gene with recurrent truncating de novo mutations in this cohort. All mutations resulted in premature termination codons in the last exon of ZNF148. The number of the de novo truncating mutations in the ZNF148 gene was significantly enriched (p = 5.42 × 10−3). The newly described ZNF148-associated syndrome is characterized by underdevelopment of the corpus callosum, mild to moderate developmental delay and ID, variable microcephaly or mild macrocephaly, short stature, feeding problems, facial dysmorphisms, and cardiac and renal malformations. We propose ZNF148 as a gene involved in a newly described ID syndrome with a recurrent phenotype and postulate that the ZNF148 is a hitherto unrecognized but crucial transcription factor in the development of the corpus callosum. Our study illustrates the advantage of whole exome sequencing in a large cohort using a parent–offspring trio approach for identifying novel genes involved in rare human diseases.
24 June 2018 in Journal of Assisted Reproduction and Genetics
Congenital disorders of glycosylation (CDG) are a growing group of inborn metabolic disorders with multiorgan presentation. SLC39A8‐CDG is a severe subtype caused by biallelic mutations in the manganese transporter SLC39A8, reducing levels of this essential cofactor for many enzymes including glycosyltransferases. The current diagnostic standard for disorders of N‐glycosylation is the analysis of serum transferrin. Exome and Sanger sequencing were performed in two patients with severe neurodevelopmental phenotypes suggestive of CDG. Transferrin glycosylation was analyzed by high‐performance liquid chromatography (HPLC) and isoelectric focusing in addition to comprehensive N‐glycome analysis using matrix‐assisted laser desorption ionization time of flight (MALDI‐TOF) mass spectrometry (MS). Atomic absorption spectroscopy was used to quantify whole blood manganese levels. Both patients presented with a severe, multisystem disorder, and a complex neurological phenotype. Magnetic resonance imaging (MRI) revealed a Leigh‐like syndrome with bilateral T2 hyperintensities of the basal ganglia. In patient 1, exome sequencing identified the previously undescribed homozygous variant c.608T>C [p.F203S] in SLC39A8. Patient 2 was found to be homozygous for c.112G>C [p.G38R]. Both individuals showed a reduction of whole blood manganese, though transferrin glycosylation was normal. N‐glycome using MALDI‐TOF MS identified an increase of the asialo‐agalactosylated precursor N‐glycan A2G1S1 and a decrease in bisected structures. In addition, analysis of heterozygous CDG‐allele carriers identified similar but less severe glycosylation changes. Despite its reliance as a clinical gold standard, analysis of transferrin glycosylation cannot be categorically used to rule out SLC39A8‐CDG. These results emphasize that SLC39A8‐CDG presents as a spectrum of dysregulated glycosylation, and MS is an important tool for identifying deficiencies not detected by conventional methods.
25 November 2014 in American Journal of Medical Genetics Part C: Seminars in Medical Genetics
Myhre syndrome (MIM #139210) is a rare multisystem disorder first described in 1981, characterized by short stature, neurodevelopmental delay, joint contractures, and cardiopulmonary complications. Its molecular basis, recurrent pathogenic variants in SMAD4, was not discovered until 2011. This narrative is based on a review of medical records, personal experiences in the care of a remarkable patient, and family interviews. It traces the life of a young man from rural Montana whose diagnosis was delayed for over two decades, despite early evaluations by renowned specialists. The absence of a unifying diagnosis profoundly shaped his and his family's experience—emotionally, medically, and socially. When the diagnosis of Myhre syndrome was finally established via whole exome sequencing in adulthood, it brought both clarity and new uncertainties. Through his story, we examine the psychosocial toll of diagnostic delay, the transformative potential of genomic medicine, and the resilience of individuals and families living with complex, undiagnosed conditions. The narrative also underscores the ongoing systemic barriers to care and inclusion for individuals with lifelong rare disorders. Lastly, this account offers a reflection on the philosophical framework of Maurice Merleau‐Ponty, whose phenomenology of the lived body versus the body‐object provides a lens to understand the subjective and embodied dimensions of living with an undiagnosed condition.