RAF1 gene fusions are recurrent driver events in infantile fibrosarcoma-like mesenchymal tumors.

Infantile fibrosarcomas (IFS) and congenital mesoblastic nephroma (CMN) are rare myofibroblastic tumors of infancy and early childhood commonly harboring the ETV6::NTRK3 gene fusion. IFS/CMN are considered as tumors with an 'intermediate prognosis' as they are locally aggressive, but rarely metastasize, and generally have a favorable outcome. A fraction of IFS/CMN-related neoplasms are negative for the ETV6::NTRK3 gene rearrangement and are characterized by other chimeric proteins promoting MAPK signaling upregulation. In a large proportion of these tumors, which are classified as IFS-like mesenchymal neoplasms, the contributing molecular events remain to be identified. Here, we report three distinct rearrangements involving RAF1 among eight ETV6::NTRK3 gene fusion-negative tumors with an original histological diagnosis of IFS/CMN. The three fusion proteins retain the entire catalytic domain of the kinase. Two chimeric products, GOLGA4::RAF1 and LRRFIP2::RAF1, had previously been reported as driver events in different cancers, whereas the third, CLIP1::RAF1, represents a novel fusion protein. We demonstrate that CLIP1::RAF1 acts as a bona fide oncoprotein promoting cell proliferation and migration through constitutive upregulation of MAPK signaling. We show that the CLIP1::RAF1 hyperactive behavior does not require RAS activation and is mediated by constitutive 14-3-3 protein-independent dimerization of the chimeric protein. As previously reported for the ETV6::NTRK3 fusion protein, CLIP1::RAF1 similarly upregulates PI3K-AKT signaling. Our findings document that RAF1 gene rearrangements represent a recurrent event in ETV6::NTRK3-negative IFS/CMN and provide a rationale for the use of inhibitors directed to suppress MAPK and PI3K-AKT signaling in these cancers. © 2024 The Pathological Society of Great Britain and Ireland.

Parkin Mutation Affects Clock Gene-Dependent Energy Metabolism.

Growing evidence highlights a tight connection between circadian rhythms, molecular clockworks, and mitochondrial function. In particular, mitochondrial quality control and bioenergetics have been proven to undergo circadian oscillations driven by core clock genes. Parkinson's disease (PD) is a chronic neurodegenerative disease characterized by a selective loss of dopaminergic neurons. Almost half of the autosomal recessive forms of juvenile parkinsonism have been associated with mutations in the PARK2 gene coding for parkin, shown to be involved in mitophagy-mediated mitochondrial quality control. The aim of this study was to investigate, in fibroblasts from genetic PD patients carrying parkin mutations, the interplay between mitochondrial bioenergetics and the cell autonomous circadian clock. Using two different in vitro synchronization protocols, we demonstrated that normal fibroblasts displayed rhythmic oscillations of both mitochondrial respiration and glycolytic activity. Conversely, in fibroblasts obtained from PD patients, a severe damping of the bioenergetic oscillatory patterns was observed. Analysis of the core clock genes showed deregulation of their expression patterns in PD fibroblasts, which was confirmed in induced pluripotent stem cells (iPSCs) and induced neural stem cells (iNSCs) derived thereof. The results from this study support a reciprocal interplay between the clockwork machinery and mitochondrial energy metabolism, point to a parkin-dependent mechanism of regulation, and unveil a hitherto unappreciated level of complexity in the pathophysiology of PD and eventually other neurodegenerative diseases.

Production of an induced pluripotent stem cell line CSSi018-A (14192) from a patient with hypomyelinating leukodystrophy 7 (HLD7) carrying biallelic variants of POLR3A (c.1802 T > A; c.4072G > A).

Hypomyelinating leukodystrophies (HLD) are a group of heterogeneous genetic disorders characterized by a deficit in myelin deposition during brain development. Specifically, 4H-Leukodystrophy is a recessive disease due to biallelic mutations in the POLR3A gene, which encodes one of the subunits forming the catalytic core of RNA polymerase III (PolIII). The disease also presents non-neurological signs such as hypodontia and hypogonadotropic hypogonadism. Here, we report the generation of a human induced pluripotent stem cell (hiPSC) line from fibroblasts of the first identified carrier of the biallelic POLR3A variants c.1802 T > A and c.4072G > A.

Corrigendum: Deepening the understanding of CNVs on chromosome 15q11-13 by using hiPSCs: An overview.

[This corrects the article DOI: 10.3389/fcell.2022.1107881.].

Generation of an induced pluripotent stem cell line CSSi015-A (9553), carrying a point mutation c.2915C > T in the human calcium sensing receptor (CasR) gene.

Familial Hypocalciuric Hypercalcemia (FHH1) is a rare autosomal dominant disease with low penetrance, caused by inactivating mutations of the calcium-sensing receptor (CaSR) gene, characterized by significant hypercalcemia, inappropriately normal serum PTH levels and a low urinary calcium level. Human induced pluripotent stem cells (hiPSCs) from a patient carrying a previously identified heterozygous mutation, a p.T972M amino acid substitution in cytoplasmic tail of CasR, were produced using a virus, xeno-free and non-integrative protocol.

Generation and characterization of CSSi016-A (9938) human pluripotent stem cell line carrying two biallelic variants in MTMR5/SBF1 gene resulting in a case of severe CMT4B3.

Charcot-Marie-Tooth type 4B3 (CMT4B3) is a rare subtype of hereditary neuropathy associated with variants in the MTMR5/SBF1 gene. Herein, we report the generation and characterization of a hiPSC line from a 12-year-old Italian girl with early onset severe polyneuropathy with motor and axonal involvement, harboring biallelic variants in the MTMR5/SBF1 gene. Fibroblasts were reprogrammed using non-integrating episomal plasmids, and iPSCs successfully passed the stemness and pluripotency tests. Patient-specific hiPSCs were produced to obtain a disease model for the study of this rare condition.

Deepening the understanding of CNVs on chromosome 15q11-13 by using hiPSCs: An overview.

The human α7 neuronal nicotinic acetylcholine receptor gene (CHRNA7) is widely expressed in the central and peripheral nervous systems. This receptor is implicated in both brain development and adult neurogenesis thanks to its ability to mediate acetylcholine stimulus (Ach). Copy number variations (CNVs) of CHRNA7 gene have been identified in humans and are genetically linked to cognitive impairments associated with multiple disorders, including schizophrenia, bipolar disorder, epilepsy, Alzheimer's disease, and others. Currently, α7 receptor analysis has been commonly performed in animal models due to the impossibility of direct investigation of the living human brain. But the use of model systems has shown that there are very large differences between humans and mice when researchers must study the CNVs and, in particular, the CNV of chromosome 15q13.3 where the CHRNA7 gene is present. In fact, human beings present genomic alterations as well as the presence of genes of recent origin that are not present in other model systems as well as they show a very heterogeneous symptomatology that is associated with both their genetic background and the environment where they live. To date, the induced pluripotent stem cells, obtained from patients carrying CNV in CHRNA7 gene, are a good in vitro model for studying the association of the α7 receptor to human diseases. In this review, we will outline the current state of hiPSCs technology applications in neurological diseases caused by CNVs in CHRNA7 gene. Furthermore, we will discuss some weaknesses that emerge from the overall analysis of the published articles.

Generation of induced pluripotent stem cell line CSSi008-A (4698) from a patient affected by advanced stage of Dentato-Rubral-Pallidoluysian atrophy (DRPLA).

Dentato-Rubral-pallidoluysian atrophy (DRPLA) is a rare autosomal, dominant, progressive neurodegenerative disease that causes involuntary movements, mental and emotional problems. DRPLA is caused by a mutation in the ATN1 gene that encodes for an abnormal polyglutamine stretch in the atrophin-1 protein. DRPLA is most common in the Japanese population, where it has an estimated incidence of 2 to 7 per million people. This condition has also been seen in families from North America and Europe. We obtained a reprogrammed iPSC line from a Caucasian patient with a juvenile onset of the disease, carrying 64 CAG repeat expansion in the ATN1 gene.

Generation of induced pluripotent stem cell line, CSSi004-A (2962), from a patient diagnosed with Huntington's disease at the presymptomatic stage.

Huntington's disease (HD) is an incurable, autosomal dominant, hereditary neurodegenerative disorder that typically manifests itself in midlife. This pathology is linked to the deregulation of multiple, as yet unknown, cellular processes starting before HD onset. A human iPS cell line was generated from skin fibroblasts of a subject at the presymptomatic life stage, carrying a polyglutamine expansion in HTT gene codifying Huntingtin protein. The iPSC line contained the expected CAG expansion, expressed the expected pluripotency markers, displayed in vivo differentiation potential to the three germ layers and had a normal karyotype.

Generation of induced pluripotent stem cell line, CSSi002-A (2851), from a patient with juvenile Huntington Disease.

Huntington Disease (HD) is an autosomal dominant disorder characterized by motor, cognitive and behavioral features caused by a CAG expansion in the HTT gene beyond 35 repeats. The juvenile form (JHD) may begin before the age of 20years and is associated with expanded alleles as long as 60 or more CAG repeats. In this study, induced pluripotent stem cells were generated from skin fibroblasts of a 8-year-old child carrying a large size mutation of 84 CAG repeats in the HTT gene. HD appeared at age 3 with mixed psychiatric (i.e. autistic spectrum disorder) and motor (i.e. dystonia) manifestations.

Generation of the induced pluripotent stem cell line CSSi006-A (3681) from a patient affected by advanced-stage Juvenile Onset Huntington's Disease.

Juvenile Onset Huntington's Disease (JOHD) is a rare variant of HD withage of onset ≤20 years, accounting for 3-10% of all HD patients. The rarity occurrence of JOHD cases, who severely progress towards mental and physical disability with atypical clinical manifestations compared to classical HD, are responsible of general lack of knowledge about this variant. We obtained a fully reprogrammed iPS cell line from fibroblasts of a JOHD patient carrying 65 CAG repeats and age at onset at age 15. At the biopsy time, the patient showed an advanced stage after 10 years of disease.