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Chromosome 8p is a rare genetic condition with approximately 350 patients around the world and counting. A chromosome disorder typically impacts every cell in your body, not just in one organ of your body, but often your entire human system. Right now, science does not have the means to treat this condition. The good news is that the scientific community is making substantial progress and together with Project 8p, we are going to do everything we can to help.
Associated symptoms and findings may vary greatly in range and severity from case to case. Intellectual disability, congenital heart defects, epilepsy, autism, agenesis of corpus collosum, and sensory processing disorders are some of the diagnoses found with a Chromosome 8p karyotype. Common features include growth deficiency; cognitive impairments; mild malformations of the skull and facial (craniofacial) region, such as a small head (microcephaly) and vertical skin folds that may cover the eyes inner corners (epicanthal folds); heart (cardiac) abnormalities. Additional craniofacial features may also be present that tend to become less apparent with age, such as a short, broad nose; a low, wide nasal bridge; and/or a small jaw (micrognathia).
The majority of 8p individuals have developmental delays including disordered acquisition of cognitive and social competence and delays in reaching developmental milestones.
In most cases, Chromosome 8, appears to result from spontaneous (de novo) errors very early in embryonic development that occur for unknown reasons and are not inherited. Recently, we have found families where the mutation has also been inherited but different manifestations of the symptoms.
What is a chromosomal disorder?
Chromosomal rearrangements (also known as copy number variants) can occur with the number of chromosomes or the structure of a chromosome such as:
- Monosomy – A person has only one copy of a chromosome. In a partial monosomy, only part of one chromosome is missing.
- Trisomy – A person has three copies of a chromosome. Partial trisomy means a person has an extra copy of part of a chromosome.
- Deletions– A section of a chromosome is missing. This can be referred to as a deletion, partial deletion, partial monosomy, distal monosomy or terminal deletion.
- Duplications – Part of the chromosome is duplicated so a person has extra genetic material.
- Translocations – A section of one chromosome is transferred to a different chromosome.
- Rings – A portion of a chromosome has broken and formed into a ring shape. This can happen with or without loss of genetic material.
- Mosaicism – Mosaicism occurs when a person has two or more cell populations with a different chromosomal makeup. When abnormalities occur after fertilization, mosaicism can occur because some cells have the abnormality and some do not.
- Isochromosome -This occurs with improper division of the centromere. Isochromosomes contain either two short arms or two long arms, instead one short arm and one long arm, like a typical chromosome.
- Inversion – Part of a chromosome has broken off, turned upside down and reattached itself. Inversions can be paracentric or pericentric. Paracentric inversions occur on only one arm of the chromosome and do not include the centromere. Pericentric inversions include the centromere and include both arms of the chromosome.
There are many synonyms of Chromosome 8 diagnoses:
- 8p – Syndrome, Partial
- Chromosome 8p inv/del/dup
- Chromosome 8, 8p Deletion or Del(8p) Syndrome, Partial
- Chromosome 8, Partial Deletion of Short Arm
- Chromosome 8, Partial Monosomy 8p
- Chromosome 8, 8p Duplication or Dup(8p) Syndrome, Partial
- Distal 8p Monosomy
- Partial 8p Monosomy
- Terminal 8p- Syndrome (8p21 to 8p23-pter), Included
- Trisomy 8p
- Mosaicism 8p
On the entire chromosome 8 (including the short arm 8p and the long arm 8q), these are some known disorders/syndromes:
- Burkitt’s lymphoma – translocation on 8 with the myc gene
- Charcot-Marie-Tooth disease and type 2 and type 4
- Cleft lip and palate
- Cohen syndrome
- Congenital hypothyroidism
- Fahr’s syndrome – a loss of function mutation in the gene encoding type III sodium dependent phosphate transporter 2(SLC20A2) located on chromosome 8 has also been reported as the molecular level to form the genetic basis for the pathophysiology of this disease
- Roberts Syndrome – caused by disruptions or changes of the ESCO2 (establishment of cohesion 1 homolog 2) gene located on the short arm (p) of chromosome 8 (8p21.1)
- Hereditary Multiple Exostoses
- Lipoprotein lipase deficiency, familial
- Pfeiffer syndrome
- Primary microcephaly
- Rothmund-Thomson syndrome, or poikiloderma congenitale
- Schizophrenia, associated with 8p21-22 locus
- Waardenburg syndrome
- Werner syndrome
- Pingelapese blindness
- Langer-Giedion syndrome
Fun Fact: Parts of chromosome 8 have a high rate of mutation and it is one of the chromosomes that differs the most from chimpanzees. Mutations on chromosome 8 may be partially responsible for humans’ large brains so human intelligence can be at least partially traced to people who have mutations and abnormalities on chromosome 8. Chromosomal mutations and abnormalities occur naturally and are the vehicle by which evolution is possible.
Genes in Chromosome 8:
Chromosomes are the structures that hold genes. Scientists are working to decipher what every gene on the human genome does, but they still have a lot to learn. This unique genotype is a complete set instructions that help the body synthesize proteins. The genotype dictates how the body is supposed to be built and function. This results in specific and unique physical and medical characteristics for every human being.
- The Human Genome Project has revealed that there are probably about 20,000-25,000 ‘haploid’ protein coding genes.
- Chromosome 8 contains around 4.5 to 5 percent of the total DNA in cells, which is probably around 700 genes up to 1400 genes.
- Chromosome 8 contains about 146 million base pairs or DNA building blocks, of which over 95% have been determined
The following are some of the genes located on chromosome 8:
- AEG1 : Astrocyte Elevated Gene (linked to hepatocellular carcinoma and neuroblastoma)
- Arc/Arg3.1
- COH1
- FGFR1: fibroblast growth factor receptor 1 (fms-related tyrosine kinase 2, Pfeiffer syndrome)
- GDAP1: ganglioside-induced differentiation-associated protein 1
- LPL: lipoprotein lipase
- MCPH1: microcephaly, primary autosomal recessive 1
- NDRG1: N-myc downstream regulated gene 1
- NEF3: neurofilament 3 (150kDa medium)
- NEFL: neurofilament, light polypeptide 68kDa
- SLC20A2: Sodium-dependent phosphate transporter 2
- SNAI2: snail homolog 2 (Drosophila)
- TG: thyroglobulin
- TPA: tissue plasminogen activator
- VMAT1: vesicular monoamine transporter protein
- WRN: Werner syndrome
- GULOP pseudogene: responsible for human inability to produce Vitamin C
Inversion/Duplication/Deletion
