Fragile X syndrome (FXS) is a genetic disorder characterized by mild-to-moderate intellectual disability. The average IQ in males with FXS is under 55, while about two thirds of affected females are intellectually disabled. Physical features may include a long and narrow face, large ears, flexible fingers, and large testicles. About a third of those affected have features of autism such as problems with social interactions and delayed speech. Hyperactivity is common, and seizures occur in about 10%. Males are usually more affected than females.
Helicases are a class of enzymes thought to be vital to all organisms. Their main function is to unpack an organism's genetic material. Helicases are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two hybridized nucleic acid strands, using energy from ATP hydrolysis. There are many helicases, representing the great variety of processes in which strand separation must be catalyzed. Approximately 1% of eukaryotic genes code for helicases.
FMR1 is a human gene that codes for a protein called fragile X messenger ribonucleoprotein, or FMRP. This protein, most commonly found in the brain, is essential for normal cognitive development and female reproductive function. Mutations of this gene can lead to fragile X syndrome, intellectual disability, premature ovarian failure, autism, Parkinson's disease, developmental delays and other cognitive deficits. The FMR1 premutation is associated with a wide spectrum of clinical phenotypes that affect more than two million people worldwide.
Alpha-thalassemia mental retardation syndrome (ATRX), also called alpha-thalassemia X-linked intellectual disability syndrome, nondeletion type or ATR-X syndrome, is an X-linked recessive condition associated with a mutation in the ATRX gene. Males with this condition tend to be moderately intellectually disabled and have physical characteristics including coarse facial features, microcephaly, hypertelorism, a depressed nasal bridge, a tented upper lip and an everted lower lip. Mild or moderate anemia, associated with alpha-thalassemia, is part of the condition. Females with this mutated gene have no specific signs or features, but if they do, they may demonstrate skewed X chromosome inactivation.
Transcriptional regulator ATRX also known as ATP-dependent helicase ATRX, X-linked helicase II, or X-linked nuclear protein (XNP) is a protein that in humans is encoded by the ATRX gene.
Fragile X mental retardation syndrome-related protein 1 is a protein that in humans is encoded by the FXR1 gene.
Polyglutamine-binding protein 1 (PQBP1) is a protein that in humans is encoded by the PQBP1 gene.
Sodium- and chloride-dependent creatine transporter 1 is a protein that in humans is encoded by the SLC6A8 gene.
Fragile X mental retardation syndrome-related protein 2 is a protein that in humans is encoded by the FXR2 gene.
AF4/FMR2 family member 2 is a protein that in humans is encoded by the AFF2 gene. Mutations in AFF2 are implicated in cases of breast cancer.
Oligophrenin-1 is a protein that in humans is encoded by the OPHN1 gene.
Putative ribosomal RNA methyltransferase 1 is an enzyme that in humans is encoded by the FTSJ1 gene.
PHD finger protein 8 is a protein that in humans is encoded by the PHF8 gene.
FG syndrome (FGS) is a rare genetic syndrome caused by one or more recessive genes located on the X chromosome and causing physical anomalies and developmental delays. FG syndrome was named after the first letters of the surnames of the first patients noted with the disease. First reported by American geneticists John M. Opitz and Elisabeth G. Kaveggia in 1974, its major clinical features include intellectual disability, hyperactivity, hypotonia, and a characteristic facial appearance including macrocephaly.
Lujan–Fryns syndrome (LFS) is an X-linked genetic disorder that causes mild to moderate intellectual disability and features described as Marfanoid habitus, referring to a group of physical characteristics similar to those found in Marfan syndrome. These features include a tall, thin stature and long, slender limbs. LFS is also associated with psychopathology and behavioral abnormalities, and it exhibits a number of malformations affecting the brain and heart. The disorder is inherited in an X-linked dominant manner, and is attributed to a missense mutation in the MED12 gene. There is currently no treatment or therapy for the underlying MED12 malfunction, and the exact cause of the disorder remains unclear.
Renpenning's syndrome is a neurodevelopmental disorder recognised in males that causes intellectual disability, mild growth retardation with examples in the testes and head, and a somewhat short stature. The condition only affects males, starting at birth.
Mental retardation and microcephaly with pontine and cerebellar hypoplasia (MICPCH) – also known as mental retardation, X-linked, syndromic, Najm type (MRXSNA); X-linked intellectual deficit, Najm type; intellectual developmental disorder, X-linked, syndromic, Najm type; X-linked intellectual disability–microcephaly–pontocerebellar hypoplasia syndrome; and by variations of these terms – is a rare X-linked dominant genetic disorder of infants characterised by intellectual disability and pontocerebellar hypoplasia. It usually affects females; many males die before birth or not long after.
MECP2 duplication syndrome (M2DS) is a rare disease that is characterized by severe intellectual disability and impaired motor function. It is an X-linked genetic disorder caused by the overexpression of MeCP2 protein.
Xp11.2 duplication is a genomic variation marked by the duplication of an X chromosome region on the short arm p at position 11.2, defined by standard karyotyping (G-banding). This gene-rich, rearrangement prone region can be further divided into three loci - Xp11.21, Xp11.22 and Xp11.23. The duplication could involve any combination of these three loci. While the length of the duplication can vary from 0.5Mb to 55 Mb, most duplications measure about 4.5Mb and typically occur in the region of 11.22-11.23. Most affected females show preferential activation of the duplicated X chromosome. Features of affected individuals vary significantly, even among members of the same family. The Xp11.2 duplication can be 'silent' - presenting no obvious symptoms in carriers - which is known from the asymptomatic parents of affected children carrying the duplication. The common symptoms include intellectual disabilities, speech delay and learning difficulties, while in rare cases, children have seizures and a recognizable brain wave pattern when assessed by EEG (electroencephalography).
AF4/FMR2 (AFF) is a family of nuclear transcriptional activators that encourage RNA elongation. There are four genes in this family, all of which reside in the nucleus of the cells. The gene family includes AFF1/AF4, AFF2/FMR2, AFF3/LAF4 and AFF4/AF5q31. Within the family, the AFF2/FMR2 is silenced in FRAXE intellectual disability; while the other three gene families will form fusion genes as a consequence of chromosome translocations with the myeloid/lymphoid or mixed lineage leukemia gene in acute lymphoblastic leukemias. While different members of the AF4/FMR2 family are known for playing various roles in cells, they all commonly participate in the regulation of splicing and transcription.
