Biomaterial Database

Twin sisters, monozygotic with the fragile X mutation, but with a different phenotype. 2000

R Willemsen, and R Olmer, and Y De Diego Otero, and B A Oostra

CBG Department of Clinical Genetics, Erasmus University, Rotterdam, The Netherlands.

The absence of the fragile X mental retardation protein (FMRP) results in fragile X syndrome. All males with a full mutation in the FMR1 gene and an inactive FMR1 gene are mentally retarded while 60% of the females with a full mutation are affected. Here we describe monozygotic twin sisters who both have a full mutation in their FMR1 gene, one of whom is normal while the other is affected. Using molecular and protein studies it was shown that owing to preferential X inactivation in the affected female a minority of the cells expressed the normal FMR1 gene, while in her sister most cells expressed the normal FMR1 gene. This shows that X inactivation took place in the female twins after separation of the embryos and that for a normal phenotype FMR1 expression is necessary in the majority of cells.

UI	MeSH Term	Description	Entries
D008607	Intellectual Disability	Subnormal intellectual functioning which originates during the developmental period. This has multiple potential etiologies, including genetic defects and perinatal insults. Intelligence quotient (IQ) scores are commonly used to determine whether an individual has an intellectual disability. IQ scores between 70 and 79 are in the borderline range. Scores below 67 are in the disabled range. (from Joynt, Clinical Neurology, 1992, Ch55, p28)	Disability, Intellectual,Idiocy,Mental Retardation,Retardation, Mental,Deficiency, Mental,Intellectual Development Disorder,Mental Deficiency,Mental Retardation, Psychosocial,Deficiencies, Mental,Development Disorder, Intellectual,Development Disorders, Intellectual,Disabilities, Intellectual,Disorder, Intellectual Development,Disorders, Intellectual Development,Intellectual Development Disorders,Intellectual Disabilities,Mental Deficiencies,Mental Retardations, Psychosocial,Psychosocial Mental Retardation,Psychosocial Mental Retardations,Retardation, Psychosocial Mental,Retardations, Psychosocial Mental
D009419	Nerve Tissue Proteins		Proteins, Nerve Tissue,Tissue Proteins, Nerve
D010641	Phenotype	The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.	Phenotypes
D005260	Female		Females
D005600	Fragile X Syndrome	A condition characterized genotypically by mutation of the distal end of the long arm of the X chromosome (at gene loci FRAXA or FRAXE) and phenotypically by cognitive impairment, hyperactivity, SEIZURES, language delay, and enlargement of the ears, head, and testes. INTELLECTUAL DISABILITY occurs in nearly all males and roughly 50% of females with the full mutation of FRAXA. (From Menkes, Textbook of Child Neurology, 5th ed, p226)	FRAXA Syndrome,FRAXE Syndrome,Martin-Bell Syndrome,Fra(X) Syndrome,Fragile X Mental Retardation Syndrome,Fragile X-F Mental Retardation Syndrome,Mar (X) Syndrome,Marker X Syndrome,Mental Retardation, X-Linked, Associated With Fragile Site Fraxe,Mental Retardation, X-Linked, Associated With Marxq28,X-Linked Mental Retardation and Macroorchidism,FRAXA Syndromes,FRAXE Syndromes,Fragile X Syndromes,Marker X Syndromes,Martin Bell Syndrome,Syndrome, FRAXA,Syndrome, FRAXE,Syndrome, Fragile X,Syndrome, Marker X,Syndrome, Martin-Bell,Syndromes, FRAXA,Syndromes, FRAXE,Syndromes, Fragile X,Syndromes, Marker X,X Linked Mental Retardation and Macroorchidism
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D014430	Twins, Monozygotic	Two off-spring from the same PREGNANCY. They are from a single fertilized OVUM that split into two EMBRYOS. Such twins are usually genetically identical and of the same sex.	Twins, Identical,Identical Twin,Identical Twins,Monozygotic Twin,Monozygotic Twins,Twin, Identical,Twin, Monozygotic
D016601	RNA-Binding Proteins	Proteins that bind to RNA molecules. Included here are RIBONUCLEOPROTEINS and other proteins whose function is to bind specifically to RNA.	Double-Stranded RNA-Binding Protein,Double-Stranded RNA-Binding Proteins,ds RNA-Binding Protein,RNA-Binding Protein,ds RNA-Binding Proteins,Double Stranded RNA Binding Protein,Double Stranded RNA Binding Proteins,Protein, Double-Stranded RNA-Binding,Protein, ds RNA-Binding,RNA Binding Protein,RNA Binding Proteins,RNA-Binding Protein, Double-Stranded,RNA-Binding Protein, ds,RNA-Binding Proteins, Double-Stranded,ds RNA Binding Protein
D051860	Fragile X Mental Retardation Protein	A RNA-binding protein that is found predominately in the CYTOPLASM. It helps regulate GENETIC TRANSLATION in NEURONS and is absent or under-expressed in FRAGILE X SYNDROME.	FMRP Protein,Fragile X Mental Retardation-1 Protein,Fragile X Mental Retardation 1 Protein