Researches have shown the correlations of fragile X syndrome with delinquencies, cognitive and behavioral problems such as anxiety, attention deficit, communication disturbances, hyperactivity in children, and anti-social behaviors (Reiss and Scott 664). While males most often exhibit social avoidance, aggression, communication abnormalities, and even self-injurious behavior, females show attention deficit, anti-social behavior, emotional disturbances, depression, and maladaptive behaviors (Reiss and Scott 664).
Brain Structure and Function Through brain images of fragile X patients, characteristic abnormalities brought by fragile X syndrome on the morphology of the brain were described and identified. Generally, individuals affected by fragile X have volumetric enlargement of caudate nucleus and volume decreased on cerebellar vermis, superior temporal gyrus, and amygdala regions (Reiss and Scott 666). Furthermore, within parietal and prefrontal-caudate regions, fractional anisotropy reductions were observed (Reiss and Scott 666).
These aberrations then greatly caused impairments on the physiological processes of the brain that directly influence the cognitive and affective attributes of the affected individuals. Brain Anatomy, Gender and IQ in Children and Adolescent with Fragile X Syndrome The brain has sensitive and complicated sequence of developmental process which includes synaptic elimination, myelination, cellular proliferation, apoptosis, and neuropil growth (Eliez et al. 1610).
It was estimated that for every 2000-6000 live births, a single case would arise with a gene mutation that changes the course of the normal developmental processes resulting to the fragile X syndrome (Eliez et al. 1610). Fragile X syndrome, a genetic disorder, is the well-known cause of genetic inheritance of mental retardation. This genetic mutation interferes with the brain pathways for cognitive, physical, and behavioral developments (Eliez et al. 1610).
As such, dysmorphic ears, prominent jaw, and a narrow and long face as well as macroochidism physically observed among the affected individuals; however, variation on their physical appearances specifically during the period of puberty among females makes the diagnosis, based merely on physical attributes, difficult (Eliez et al. 1610). Meanwhile, the consistency of behavioral and cognitive effects of the syndrome signified the predisposition of the genetic trait aberration in all cases.
Also, affected males exhibit phenotypic characteristics differently from the inflicted females which denoted that the genetic defect is linked to the X-chromosome. For instance, in full heterozygous mutation, Females exhibit non-severe mental retardation with normal cognitive capability amidst learning difficulties (Eliez et al. 1610). They also experience anxiety, peer-interaction difficulties and attention deficit (Eliez et al. 1610).
Likewise, Males with full hemizygous fragile X genetic defect exhibit moderate to severe mental retardation which impairs short-term memory, visuospatial abilities, and visual-motor coordination (Eliez et al. 1611). They also have motor stereotypes, socialization difficulties, hyperactivity, gaze avoidance, and autistic characteristics (Eliez et al. 1611). However, this phenotypic attributes can also be observed in other genetic disorder like autism, thus, are not the exclusive bases of fragile X detection (Eliez et al. 1611).
Early studies on fragile X revealed that the phenotypical characteristics were imparted by X-chromosome abnormality (Eliez et al. 1611). Specifically, the determinant mutation of fragile X syndrome was reported in 1991 and identified as the repetition of CGG in expanded number. The chromosome incurs CGG triplet repeats initially at the untranslated region, 5’, of the FMRI gene (Eliez et al. 1611). As the CGG reaches higher than 200 repeats, hypermethylation can possibly occur at the FMR1 promoter portion which in turn hinders the FMR1 transcription and translation leading to the gene’s transcriptional silence (Eliez et al. 1611).
This reduction of FMR1 due to transcriptional silence, even though only few researches delved on the neuroanatomical implications of the mutation, can result to faulty functions and development of the brain (Eliez et al. 1611). As such, studies showed that FMR1 mRNA has links to neuronal localization and expression of gene brain areas such as nucleus basalis, hippocampus, and cerebellum with respect to the development of mammals (Eliez et al. 1611).