Mendeliome
Gene: FBN2 Green List (high evidence)Green List (high evidence)
The association between mono-allelic variants in FBN2 and CCA is well established. Recent report of bi-allelic variants, Kloth (2021): biallelic FBN2 variants (PTC/missense) in a teenager with severe CCA, including cardiac defects, mild scoliosis and muscular involvement. Carrier parents both "healthy/unaffected". Phenotype matches mouse K/O. Authors performed a lit review and identified an additional 2 homozygous patients (both missense variants) with - fetal akinesia, brain ischemia and neonatal death - severe muscle weakness with bilateral clubfeet, a pronounced gait disturbance, recurrent patellar dislocations, flexion contractures, camptodactyly, widespread striae and an unusual myofibrillar disorganization, variation in fiber size and atrophic fibers in muscle biopsy.
Evidence for association with Macular degeneration, early-onset MIM#616118 is limited. One family reported, plus some rare variants reported in cohort studies. The familial variant p.Glu1144Lys is present in 11 hets in gnomad and has benign in silicos. The second variant reported in the paper, p.Met1247Thr is present in >20 hets.Created: 9 Apr 2021, 4:08 a.m. | Last Modified: 9 Apr 2021, 4:08 a.m.
Panel Version: 0.7084
Comment when marking as ready: The gene-disease association with Contractual arachnodactyly is extremely well established. The gene-disease association with macular degeneration much less so. There are ~4 families reported in the literature, and some discussion about whether the contribution of rare FBN2 variants in this context are under a 'monogenic' or 'polygenic' model.Created: 31 Mar 2020, 12:47 a.m. | Last Modified: 31 Mar 2020, 12:47 a.m.
Panel Version: 0.1850
Mode of inheritance
BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Phenotypes
Contractural arachnodactyly, congenital MIM#121050; Macular degeneration, early-onset MIM#616118
Publications
Green List (high evidence)
Variants in the EGF-repeat domains of FBN1/FBN2, specifically involving cysteine (involved in disulphide binding) are commonly reported.
Highly homologous to FBN1Created: 29 Mar 2020, 8:27 p.m. | Last Modified: 29 Mar 2020, 8:27 p.m.
Panel Version: 0.1842
Mode of inheritance
MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown
Phenotypes
Contractural arachnodactyly, congenital 121050; Macular degeneration, early-onset 616118
Publications
Variants in this GENE are reported as part of current diagnostic practice
Publications for gene: FBN2 were set to 19473076; 11068201; 27007659; 24899048
Mode of inheritance for gene: FBN2 was changed from MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted to BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Gene: fbn2 has been classified as Green List (High Evidence).
Publications for gene: FBN2 were set to 19473076; 11068201
Phenotypes for gene: FBN2 were changed from to Contractural arachnodactyly, congenital 121050; Macular degeneration, early-onset 616118
Publications for gene: FBN2 were set to
Mode of inheritance for gene: FBN2 was changed from Unknown to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
gene: FBN2 was added gene: FBN2 was added to Mendeliome_VCGS. Sources: Expert Review Green,Victorian Clinical Genetics Services Mode of inheritance for gene: FBN2 was set to Unknown
If promoting or demoting a gene, please provide comments to justify a decision to move it.
Genes included in a Genomics England gene panel for a rare disease category (green list) should fit the criteria A-E outlined below.
These guidelines were developed as a combination of the ClinGen DEFINITIVE evidence for a causal role of the gene in the disease(a), and the Developmental Disorder Genotype-Phenotype (DDG2P) CONFIRMED DD Gene evidence level(b) (please see the original references provided below for full details). These help provide a guideline for expert reviewers when assessing whether a gene should be on the green or the red list of a panel.
A. There are plausible disease-causing mutations(i) within, affecting or encompassing an interpretable functional region(ii) of this gene identified in multiple (>3) unrelated cases/families with the phenotype(iii).
OR
B. There are plausible disease-causing mutations(i) within, affecting or encompassing cis-regulatory elements convincingly affecting the expression of a single gene identified in multiple (>3) unrelated cases/families with the phenotype(iii).
OR
C. As definitions A or B but in 2 or 3 unrelated cases/families with the phenotype, with the addition of convincing bioinformatic or functional evidence of causation e.g. known inborn error of metabolism with mutation in orthologous gene which is known to have the relevant deficient enzymatic activity in other species; existence of an animal model which recapitulates the human phenotype.
AND
D. Evidence indicates that disease-causing mutations follow a Mendelian pattern of causation appropriate for reporting in a diagnostic setting(iv).
AND
E. No convincing evidence exists or has emerged that contradicts the role of the gene in the specified phenotype.
(i)Plausible disease-causing mutations: Recurrent de novo mutations convincingly affecting gene function. Rare, fully-penetrant mutations - relevant genotype never, or very rarely, seen in controls. (ii) Interpretable functional region: ORF in protein coding genes miRNA stem or loop. (iii) Phenotype: the rare disease category, as described in the eligibility statement. (iv) Intermediate penetrance genes should not be included.
It’s assumed that loss-of-function variants in this gene can cause the disease/phenotype unless an exception to this rule is known. We would like to collect information regarding exceptions. An example exception is the PCSK9 gene, where loss-of-function variants are not relevant for a hypercholesterolemia phenotype as they are associated with increased LDL-cholesterol uptake via LDLR (PMID: 25911073).
If a curated set of known-pathogenic variants is available for this gene-phenotype, please contact us at panelapp@genomicsengland.co.uk
We classify loss-of-function variants as those with the following Sequence Ontology (SO) terms:
Term descriptions can be found on the PanelApp homepage and Ensembl.
If you are submitting this evaluation on behalf of a clinical laboratory please indicate whether you report variants in this gene as part of your current diagnostic practice by checking the box
Standardised terms were used to represent the gene-disease mode of inheritance, and were mapped to commonly used terms from the different sources. Below each of the terms is described, along with the equivalent commonly-used terms.
A variant on one allele of this gene can cause the disease, and imprinting has not been implicated.
A variant on the paternally-inherited allele of this gene can cause the disease, if the alternate allele is imprinted (function muted).
A variant on the maternally-inherited allele of this gene can cause the disease, if the alternate allele is imprinted (function muted).
A variant on one allele of this gene can cause the disease. This is the default used for autosomal dominant mode of inheritance where no knowledge of the imprinting status of the gene required to cause the disease is known. Mapped to the following commonly used terms from different sources: autosomal dominant, dominant, AD, DOMINANT.
A variant on both alleles of this gene is required to cause the disease. Mapped to the following commonly used terms from different sources: autosomal recessive, recessive, AR, RECESSIVE.
The disease can be caused by a variant on one or both alleles of this gene. Mapped to the following commonly used terms from different sources: autosomal recessive or autosomal dominant, recessive or dominant, AR/AD, AD/AR, DOMINANT/RECESSIVE, RECESSIVE/DOMINANT.
A variant on one allele of this gene can cause the disease, however a variant on both alleles of this gene can result in a more severe form of the disease/phenotype.
A variant in this gene can cause the disease in males as they have one X-chromosome allele, whereas a variant on both X-chromosome alleles is required to cause the disease in females. Mapped to the following commonly used term from different sources: X-linked recessive.
A variant in this gene can cause the disease in males as they have one X-chromosome allele. A variant on one allele of this gene may also cause the disease in females, though the disease/phenotype may be less severe and may have a later-onset than is seen in males. X-linked inactivation and mosaicism in different tissues complicate whether a female presents with the disease, and can change over their lifetime. This term is the default setting used for X-linked genes, where it is not known definitately whether females require a variant on each allele of this gene in order to be affected. Mapped to the following commonly used terms from different sources: X-linked dominant, x-linked, X-LINKED, X-linked.
The gene is in the mitochondrial genome and variants within this can cause this disease, maternally inherited. Mapped to the following commonly used term from different sources: Mitochondrial.
Mapped to the following commonly used terms from different sources: Unknown, NA, information not provided.
For example, if the mode of inheritance is digenic, please indicate this in the comments and which other gene is involved.