Forkhead Box G1 Gene Research Articles

Paving Therapeutic Avenues for FOXG1 Syndrome: Untangling Genotypes and Phenotypes from a Molecular Perspective.

Development of the central nervous system (CNS) depends on accurate spatiotemporal control of signaling pathways and transcriptional programs. Forkhead Box G1 (FOXG1) is one of the master regulators that play fundamental roles in forebrain development; from the timing of neurogenesis, to the patterning of the cerebral cortex. Mutations in the FOXG1 gene cause a rare neurodevelopmental disorder called FOXG1 syndrome, also known as congenital form of Rett syndrome. Patients presenting with FOXG1 syndrome manifest a spectrum of phenotypes, ranging from severe cognitive dysfunction and microcephaly to social withdrawal and communication deficits, with varying severities. To develop and improve therapeutic interventions, there has been considerable progress towards unravelling the multi-faceted functions of FOXG1 in the neurodevelopment and pathogenesis of FOXG1 syndrome. Moreover, recent advances in genome editing and stem cell technologies, as well as the increased yield of information from high throughput omics, have opened promising and important new avenues in FOXG1 research. In this review, we provide a summary of the clinical features and emerging molecular mechanisms underlying FOXG1 syndrome, and explore disease-modelling approaches in animals and human-based systems, to highlight the prospects of research and possible clinical interventions.

Genotype-phenotype implications from three representative clinical FOXG1 variants associated with FOXG1 syndrome

FOXG1 (Forkhead Box G1) gene, as its name indicates, encodes a transcription factor with a Forkhead DNA-binding domain. FoxG1 protein is highly conserved among mammalian and reptilian species, with DNA-binding and C-terminal domains showing highest conservation, whereas its N-terminal domain contains a mammal-specific extended proline- and glutamine-rich region [1]. The neurodevelopmental disorder associated with heterozygous variants in FOXG1 gene is referred as FOXG1 syndrome (OMIM #613454), equivalent to the original designation of “congenital variant of Rett syndrome.” [2] The main clinical features of FOXG1 syndrome include, but are not limited to, impairment of postnatal growth, primary or secondary microcephaly, severe intellectual disability with absent speech development, epilepsy, stereotypies, and dyskinesia [3].

A Forkhead box G1 (FOXG1) gene mutation in an Indian patient with a congenital variant of Rett syndrome.

A congenital variant of rett syndrome or Forkhead box G1 (FOXG1) syndrome is a rareneurodevelopmental disorder characterized by global developmental delay, microcephaly, autisticfeatures, early-onset dyskinesia, and seizures. Once it was described as one atypical variant of rettsyndrome but now considered as a separate entity. The current study found one girl carrying the denovo c.500-501incG frameshift mutation in the FOXG1 gene by genetic analysis during theevaluation for severe chronic encephalopathy. In literature, only one case was reported from Indiawith FOXG1 mutation. The FOXG1 mutation should be considered in children with a history of globaldevelopmental delay, dyskinesia, and microcephaly with characteristic brain neuroimaging findings.

The FOXG1-related syndrome with two novel mutations in the FOXG1 gene

Rett syndrome (RTT) is a rare neurological disorder with a range of clinical manifestations. Mutations in Methyl CpG binding protein 2 (MECP2) gene are found in >95% of typical form and 50–70% of atypical form of Rett syndrome. Mutations in the Cyclin-dependent kinase-like 5 (CDKL5) and Forkhead box G1 (FOXG1) genes are associated with specific RTT variants. This study was carried out to identify the gene mutations in patients with symptoms related to congenital Rett syndrome. Possible causative variations were identified using whole exome sequencing (WES) in two patients. Two novel pathogenic variants (c.563C > A, p.Ala188Glu and c.653A > G, p.Tyr218Cys) were detected in the FOXG1 gene, associated with congenital Rett syndrome. Moreover, other reported variants were also found in the KIF5A and KMT2D genes. In-silico analysis of FOXG1 variants showed that amino acid changes occurred in the conserved domain among different species that altered the conformation of FoxG1 protein; thereby, disrupting the protein function. Our findings extend the variety of mutations in the FOXG1 gene, which cause FOXG1-related syndrome.

Novel mutation in Forkhead box G1 (FOXG1) gene in an Indian patient with Rett syndrome

Rett syndrome (RTT) is a severe neurodevelopmental disorder characterized by the progressive loss of intellectual functioning, fine and gross motor skills and communicative abilities, deceleration of head growth, and the development of stereotypic hand movements, occurring after a period of normal development. The classic form of RTT involves mutation in MECP2 while the involvement of CDKL5 and FOXG1 genes has been identified in atypical RTT phenotype. FOXG1 gene encodes for a fork-head box protein G1, a transcription factor acting primarily as transcriptional repressor through DNA binding in the embryonic telencephalon as well as a number of other neurodevelopmental processes. In this report we have described the molecular analysis of FOXG1 gene in Indian patients with Rett syndrome. FOXG1 gene mutation analysis was done in a cohort of 34 MECP2/CDKL5 mutation negative RTT patients. We have identified a novel mutation (p. D263VfsX190) in FOXG1 gene in a patient with congenital variant of Rett syndrome. This mutation resulted into a frameshift, thereby causing an alteration in the reading frames of the entire coding sequence downstream of the mutation. The start position of the frameshift (Asp263) and amino acid towards the carboxyl terminal end of the protein was found to be well conserved across species using multiple sequence alignment. Since the mutation is located at forkhead binding domain, the resultant mutation disrupts the secondary structure of the protein making it non-functional. This is the first report from India showing mutation in FOXG1 gene in Rett syndrome.

A haploinsufficiency of FOXG1 identified in a boy with congenital variant of Rett syndrome

Background: Forkhead box G1 gene (FOXG1) mutations and deletions are associated with a congenital variant of Rett syndrome (RTT). Nucleotide alterations of the coding region of FOXG1 have never caused dysmorphic features. Patient: An 8-year-old boy with the congenital variant of RTT who showed severe psychomotor deterioration, epilepsy, acquired microcephaly, and involuntary movements including jerky movements of the upper limbs and tongue protrusion. He showed dysmorphic features including round face, anteverted nostrils, and tented upper lips. Brain magnetic resonance imaging showed hypoplasia of the frontal lobes and the rostral part of the corpus callosum. The molecular cytogenetic analysis confirmed a de novo deletion of 14q12 including FOXG1 in this patient. Conclusion: We identified the smallest deletion of 14q12 involving FOXG1 among those previously reported. Dysmorphic facial features are a characteristic for the patients with chromosomal deletion including FOXG1. In our patient, C14orf23 is the only transcript other than FOXG1. Therefore, C14orf23 might be responsible for facial dysmorphism.

Platelet defects in congenital variant of Rett syndrome patients with FOXG1 mutations or reduced expression due to a position effect at 14q12

The Forkhead box G1 (FOXG1) gene encodes a transcriptional repressor essential for early development of the telencephalon. Intragenic mutations and gene deletions leading to haploinsufficiency cause the congenital variant of Rett syndrome. We here describe Rett syndrome-like patients, three of them carrying a balanced translocation with breakpoint in the chromosome 14q12 region, and one patient having a 14q12 microdeletion excluding the FOXG1 gene. The hypothesis of long-range FOXG1-regulatory elements in this region was supported by our finding of reduced FOXG1 mRNA and protein levels in platelets and skin fibroblasts from these cases. Given that FOXG1 is not only expressed in brain but also in platelets, we have studied platelet morphology in these patients and two additional patients with FOXG1 mutations. Electron microscopy of their platelets showed some enlarged, rounder platelets with often abnormal alpha, and fewer dense granules. Platelet function studies were possible in one 14q12 translocation patient with a prolonged Ivy bleeding time and a patient with a heterozygous FOXG1 c.1248C>G mutation (p.Tyr416X). Both have a prolonged PFA-100 occlusion time with collagen and epinephrine and reduced aggregation responses to low dose of ADP and epinephrine. Dense granule ATP secretion was normal for strong agonists but absent for epinephrine. In conclusion, our study shows that by using platelets functional evidence of cis-regulatory elements in the 14q12 region result in reduced FOXG1 levels in patients' platelets having translocations or deletions in that region. These platelet functional abnormalities deserve further investigation regarding a non-transcriptional regulatory role for FOXG1 in these anucleated cells.

14q12 and severe Rett-like phenotypes: new clinical insights and physical mapping of FOXG1-regulatory elements

The Forkhead box G1 (FOXG1) gene has been implicated in severe Rett-like phenotypes. It encodes the Forkhead box protein G1, a winged-helix transcriptional repressor critical for forebrain development. Recently, the core FOXG1 syndrome was defined as postnatal microcephaly, severe mental retardation, absent language, dyskinesia, and dysgenesis of the corpus callosum. We present seven additional patients with a severe Rett-like neurodevelopment disorder associated with de novo FOXG1 point mutations (two cases) or 14q12 deletions (five cases). We expand the mutational spectrum in patients with FOXG1-related encephalopathies and precise the core FOXG1 syndrome phenotype. Dysgenesis of the corpus callosum and dyskinesia are not always present in FOXG1-mutated patients. We believe that the FOXG1 gene should be considered in severely mentally retarded patients (no speech-language) with severe acquired microcephaly (-4 to-6 SD) and few clinical features suggestive of Rett syndrome. Interestingly enough, three 14q12 deletions that do not include the FOXG1 gene are associated with phenotypes very reminiscent to that of FOXG1-mutation-positive patients. We physically mapped a putative long-range FOXG1-regulatory element in a 0.43 Mb DNA segment encompassing the PRKD1 locus. In fibroblast cells, a cis-acting regulatory sequence located more than 0.6 Mb away from FOXG1 acts as a silencer at the transcriptional level. These data are important for clinicians and for molecular biologists involved in the management of patients with severe encephalopathies compatible with a FOXG1-related phenotype.

Revisiting the phenotype associated with FOXG1 mutations: two novel cases of congenital Rett variant

The Forkhead box G1 (FOXG1) is a transcription factor that is critical for forebrain development, where it promotes progenitor proliferation and suppresses premature neurogenesis. Recently, the FOXG1 gene was implicated in the molecular aetiology of the congenital variant of Rett syndrome. So far, 15 FOXG1 molecular alterations, including only eight point mutations, have been reported. We screened the FOXG1 gene in a cohort of 206 MECP2 and CDKL5 mutation negative patients (136 females and 70 males) with severe encephalopathy and microcephaly. The screening was negative in all males, but two de novo mutations (c.1248C>G, p.Y416X and c.460_461dupG, p.E154GfsX300) were identified in two unrelated girls. Both patients showed neurological symptoms from the neonatal period with poor reactivity, hypotonia, and severe microcephaly. During the first year of life, both patients had feeding difficulties and made slow developmental progress. At 5 years old, the girls were significantly neurologically impaired with gross hypotonia, no language, convergent strabismus, and no voluntary hand use. Moreover, they presented a combination of jerky movements, hand-mouthing, and hand-washing stereotypies. Hence, FOXG1 mutation patients demonstrate severe encephalopathy compatible with the congenital variant, as well as additional features such as absent eye contact, inconsolable crying during the perinatal period, and delayed myelination with thin to hypoplastic corpus callosum. Although the overall frequency of mutations in FOXG1 in females with severe mental retardation and microcephaly appears to be low (1.5%), our findings suggest the requirement to investigate both point mutations and gene dosage in the FOXG1 gene in patients with severe encephalopathy with microcephaly and some Rett-like features.