9q34.3 deletion syndrome

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9q34.3 deletion syndrome
Other namesKleefstra syndrome
Specialty Medical genetics   OOjs UI icon edit-ltr-progressive.svg

9q34 deletion syndrome is a rare genetic disorder. Terminal deletions of chromosome 9q34 have been associated with childhood hypotonia, a distinctive facial appearance and developmental disability. The facial features typically described include arched eyebrows, small head circumference, midface hypoplasia, prominent jaw and a pouting lower lip. Individuals with this disease may often have speech impediments, such as speech delays. Other characteristics of this disease include: epilepsy, congenital and urogenital defects, microcephaly, corpulence, and psychiatric disorders. [1] From analysis of chromosomal breakpoints, as well as gene sequencing in suggestive cases, Kleefstra and colleagues identified EHMT1 as the causative gene. [2] This gene is responsible for producing the protein histone methyltransferase which functions to alter histones. Ultimately, histone methyltransferases are important in deactivating certain genes, needed for proper growth and development. Moreover, a frameshift, missense, or nonsense error in the coding sequence of EHMT1 can result in this condition in an individual.[ citation needed ]

Contents

Signs and symptoms

Physical symptoms

Behavioural symptoms

Genetics

Despite the associated effects of Kleefstra, there is insubstantial information regarding to the lethality of Kleefstra's. Most of the documented cases are de novo with the exception of one case due to hereditary factors; however, some cases may be a result of chromosomal translocations. In the exception case, the mother transferred the EHMT1 point mutation on to her child as she was a carrier of this gene defect. According to Mitter, et al. (2012), the mother's phenotype of the NM_024757.4:c.2712+1G>A mutation displayed mosaicism at certain tissues. This mutation resulted in the disregard of exon 18 on the EHMT1 gene, as opposed to removing it through the spliceosomes. In another transcript, however, an intron was placed between exon 18 and 19 of the EHMT1 gene. The combination of the intron insertion and the mosaicism in the mother was transferred to the child, resulting in the pathogenesis of the disease. [5]

In the past, research showed that the austerity of the disease was directly proportional to the number of EHMT1 deletions prevalent in an individual. The greater the deletions, the greater the severity of the condition. However, in recent studies, 9q34 deletion syndrome occurs when the EHMT1 gene is non-functioning, as opposed to strictly deletion. [6]

Diagnosis

Tests are either conducted at birth, or later in early childhood via: fluorescence in situ hybridization (FISH), multiplex ligation-dependent probe amplification (MLPA), array comparative genomic hybridization (aCGH), and EHMT1 sequencing. [6]

FISH is a screening test that uses multicolour probes or comparative genomic hybridization to find any chromosome irregularities in a genome. It can be used for gene mapping, detecting aneuploidy, locating tumours etc. The multicolour probes attach to a certain DNA fragment. [7] MLPA is a test that finds and records DNA copy change numbers through the use of PCR. MLPA can be used to detect tumours in the glial cells of the brain, as well as chromosomal abnormalities. [8] Array-based comparative genomic hybridization (aCGH) tracks chromosome deletions and or amplifications using fluorescent dyes on genomic sequences of DNA samples. The DNA samples (which are 25-80 base pairs in length) are then placed on slides to be observed under microscope. [9] Lastly, EHMT1 sequencing is a process in which a single-strand of DNA from the EHMT1 gene is removed, and DNA polymerase is added in order to synthesize complementary strands. In turn, this allows scientists to map out a person's DNA sequence allowing for a diagnosis to be made. [10]

Treatment

Individual manifestations are treated by a multidisciplinary team. [3]

Epidemiology

Kleefstra syndrome affects males and females equally and approximately 75% of all documented cases are caused by Eu-HMTase1 disruptions while only 25% are caused by 9q34.3 deletions. [3] There are no statistics on the effect the disease has on life expectancy due to the lack of information available. [3]

History

Kleefstra syndrome is a new condition that has only been known about for a few years and there have been fewer than 200 cases, reported. Due to the lack of cases worldwide, the history behind the origination is unclear. [11]

Research

A study published by the American Journal of Human Genetics performed an EHMT1 mutation analysis on 23 patients that showed symptoms of 9q34 deletion syndrome. The patients all varied in age. With respect to all the analyses, however, the clinical data focused on five patients, the majority being children. The first patient developed epilepsy early on in childhood, and had speech problems past age 8. He had hypoplasia and had prominent facial features, such as lips and mouth. The second patient had no trace of mitral regurgitation (MR) in her family history, but had slight hypotonia. Patient three was the oldest at 36 who began to walk at age 3. She later gained weight at eleven and developed epilepsy in her late twenties. The fourth patient had problems associated with eating as a young child and was diagnosed with slowed development. Patient five had behavioural issues and struggled with MR in addition to being overweight. The geneticists discovered three new mutations within the EHMT1 gene. The first was an interstitial deletion, while the second and third were a nonsense and frameshift. Their findings supported the notion that a disruption in the EHMT1 gene contributes to the pathogenesis of Kleefstra syndrome. [12]

In another study published by the Journal of Medical Genetics, DNA from forty patients were extracted and subjected to MLPA, FISH or EHMT1 sequencing. The forty patients were divided into two groups: 1 group of 16 patients with the 9q34 deletion, and 1 group of 24 with typical FISH/MPLA results. The geneticists examined how a missense mutation would affect the function of the DNA by looking at DNA models. After, they screened each person's DNA using one of three tests, the results for the first group showed six patients had the same deletion of the same size (700 kb). In the second group, after EHMT1 sequencing was performed, six intragenic mutations were discovered. The scientists investigating this experiment conclude these mutations may be infective agents for the disease. Lastly, the patients' behavioural, physical, and psychiatric symptoms are included on the data chart. [13]

Related Research Articles

Deletion (genetics) Mutation that removes a part of a DNA sequence

In genetics, a deletion is a mutation in which a part of a chromosome or a sequence of DNA is left out during DNA replication. Any number of nucleotides can be deleted, from a single base to an entire piece of chromosome. Some chromosomes have fragile spots where breaks occur which result in the deletion of a part of chromosome. The breaks can be induced by heat, viruses, radiations, chemicals. When a chromosome breaks, a part of it is deleted or lost, the missing piece of chromosome is referred to as deletion or a deficiency.

This is a list of topics in molecular biology. See also index of biochemistry articles.

Genetics, a discipline of biology, is the science of heredity and variation in living organisms.

DiGeorge syndrome Condition caused by a microdeletion on the long arm of chromosome 22

DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent infections, developmental delay, learning problems and cleft palate. Associated conditions include kidney problems, schizophrenia, hearing loss and autoimmune disorders such as rheumatoid arthritis or Graves' disease.

22q13 deletion syndrome Rare genetic syndrome

22q13 deletion syndrome, also known as Phelan–McDermid syndrome (PMS), is a genetic disorder caused by deletions or rearrangements on the q terminal end of chromosome 22. Any abnormal genetic variation in the q13 region that presents with significant manifestations (phenotype) typical of a terminal deletion may be diagnosed as 22q13 deletion syndrome. There is disagreement among researchers as to the exact definition of 22q13 deletion syndrome. The Developmental Synaptopathies Consortium defines PMS as being caused by SHANK3 mutations, a definition that appears to exclude terminal deletions. The requirement to include SHANK3 in the definition is supported by many but not by those who first described 22q13 deletion syndrome.

1p36 deletion syndrome Medical condition

1p36 deletion syndrome is a congenital genetic disorder characterized by moderate to severe intellectual disability, delayed growth, hypotonia, seizures, limited speech ability, malformations, hearing and vision impairment, and distinct facial features. The symptoms may vary, depending on the exact location of the chromosomal deletion.

Lymphedema–distichiasis syndrome Medical condition

Lymphedema–distichiasis syndrome is a medical condition associated with the FOXC2 gene. People with this hereditary condition have a double row of eyelashes, which is called distichiasis, and a risk of swollen limbs due to problems in the lymphatic system.

Multiplex ligation-dependent probe amplification (MLPA) is a variation of the multiplex polymerase chain reaction that permits amplification of multiple targets with only a single primer pair. It detects copy number changes at the molecular level, and software programs are used for analysis. Identification of deletions or duplications can indicate pathogenic mutations, thus MLPA is an important diagnostic tool used in clinical pathology laboratories worldwide.

2q37 deletion syndrome Medical condition

2q37 deletion syndrome is a disorder caused by the deletion of a small piece of chromosome 2 in which one or more of 3 sub-bands, 2q37.1, 2q37.2, and 2q37.3, of the last band of one of the chromosome 2’s long arms are deleted. The first report of this disorder was in 1989.

Young–Simpson syndrome Medical condition

Young–Simpson syndrome (YSS) is a rare congenital disorder with symptoms including hypothyroidism, heart defects, facial dysmorphism, cryptorchidism in males, hypotonia, mental retardation, and postnatal growth retardation.

The following outline is provided as an overview of and topical guide to genetics:

POLG Protein-coding gene in the species Homo sapiens

DNA polymerase subunit gamma is an enzyme that in humans is encoded by the POLG gene. Mitochondrial DNA polymerase is heterotrimeric, consisting of a homodimer of accessory subunits plus a catalytic subunit. The protein encoded by this gene is the catalytic subunit of mitochondrial DNA polymerase. Defects in this gene are a cause of progressive external ophthalmoplegia with mitochondrial DNA deletions 1 (PEOA1), sensory ataxic neuropathy dysarthria and ophthalmoparesis (SANDO), Alpers-Huttenlocher syndrome (AHS), and mitochondrial neurogastrointestinal encephalopathy syndrome (MNGIE).

KMT2C Protein-coding gene in the species Homo sapiens

Lysine N-methyltransferase 2C (KMT2C) also known as myeloid/lymphoid or mixed-lineage leukemia protein 3 (MLL3) is an enzyme that in humans is encoded by the KMT2C gene.

Chromothripsis Massive chromosomal rearrangement process linked to cancer

Chromothripsis is a mutational process by which up to thousands of clustered chromosomal rearrangements occur in a single event in localised and confined genomic regions in one or a few chromosomes, and is known to be involved in both cancer and congenital diseases. It occurs through one massive genomic rearrangement during a single catastrophic event in the cell's history. It is believed that for the cell to be able to withstand such a destructive event, the occurrence of such an event must be the upper limit of what a cell can tolerate and survive. The chromothripsis phenomenon opposes the conventional theory that cancer is the gradual acquisition of genomic rearrangements and somatic mutations over time.

EHMT1 Protein-coding gene in the species Homo sapiens

Euchromatic histone-lysine N-methyltransferase 1, also known as G9a-like protein (GLP), is a protein that in humans is encoded by the EHMT1 gene.

Nablus mask-like facial syndrome is a rare genetic condition. It is a microdeletion syndrome triggered by a deletion at chromosome 8 q22.1 that causes a mask-like facial appearance in those affected. This syndrome typically presents itself in infants, specifically newborns.

13q deletion syndrome Medical condition

13q deletion syndrome is a rare genetic disease caused by the deletion of some or all of the large arm of human chromosome 13. Depending upon the size and location of the deletion on chromosome 13, the physical and mental manifestations will vary. It has the potential to cause intellectual disability and congenital malformations that affect a variety of organ systems. Because of the rarity of the disease in addition to the variations in the disease, the specific genes that cause this disease are unknown. This disease is also known as:

Elective genetic and genomic testing are DNA tests performed for an individual who does not have an indication for testing. An elective genetic test analyzes selected sites in the human genome while an elective genomic test analyzes the entire human genome. Some elective genetic and genomic tests require a physician to order the test to ensure that individuals understand the risks and benefits of testing as well as the results. Other DNA-based tests, such as a genealogical DNA test do not require a physician's order. Elective testing is generally not paid for by health insurance companies. With the advent of personalized medicine, also called precision medicine, an increasing number of individuals are undertaking elective genetic and genomic testing.

Xp11.2 duplication

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).

Helsmoortel-Van der Aa syndrome Medical condition

Helsmoortel-Van der Aa syndrome is a condition caused by mutations in the activity-dependent neuroprotector homeobox (ADNP) gene. This condition is rare with <100 cases described up to 2018.

References

  1. ↑ Willemsen MH, Vulto-van Silfhout AT, Nillesen WM, Wissink-Lindhout WM, van Bokhoven H, Philip N, Berry-Kravis EM, Kini U, van Ravenswaaij-Arts CM, Delle Chiaie B, Innes AM, Houge G, Kosonen T, Cremer K, Fannemel M, Stray-Pedersen A, Reardon W, Ignatius J, Lachlan K, Mircher C, Helderman van den Enden PT, Mastebroek M, Cohn-Hokke PE, Yntema HG, Drunat S, Kleefstra T (2012). "Update on Kleefstra Syndrome". Mol Syndromol. 2 (3–5): 202–212. doi:10.1159/000335648. PMC   3366700 . PMID   22670141.
  2. ↑ Kleefstra, T (2005). "Disruption of the gene Euchromatin Histone Methyl Transferase1 (Eu-HMTase1) is associated with the 9q34 subtelomeric deletion syndrome". Journal of Medical Genetics. 42 (4): 299–306. doi:10.1136/jmg.2004.028464. ISSN   1468-6244. PMC   1736026 . PMID   15805155.
  3. 1 2 3 4 Kleefstra T, Nillesen WM, Yntema HG (7 May 2015). "Kleefstra Syndrome". Seattle:GeneReviews. GeneReviews. Retrieved 3 February 2017.
  4. ↑ Andrea Belanger, "Kleefstra Syndrome", Mommies of Miracles, 2011
  5. ↑ Rump, A; Hildebrand, L; Tzschach, A; Ullmann, R; Schrock, E; Mitter, D (August 2013). "A mosaic maternal splice donor mutation in the EHMT1 gene leads to aberrant transcripts and to Kleefstra syndrome in the offspring". European Journal of Human Genetics. 21 (8): 887–90. doi:10.1038/ejhg.2012.267. PMC   3722677 . PMID   23232695.
  6. 1 2 Rare Chromosome Disorder Support Group, "Kleefstra Syndrome" Archived 2013-07-04 at the Wayback Machine , Kleefstra Syndrome, 2009
  7. ↑ Bishop, R. (27 February 2010). "Applications of fluorescence in situ hybridization (FISH) in detecting genetic aberrations of medical significance". Bioscience Horizons. 3 (1): 85–95. doi: 10.1093/biohorizons/hzq009 .
  8. ↑ Jeuken, Judith; Cornelissen, Sandra; Boots-Sprenger, Sandra; Gijsen, Sabine; Wesseling, Pieter (September 2006). "Multiplex Ligation-Dependent Probe Amplification". The Journal of Molecular Diagnostics. 8 (4): 433–443. doi:10.2353/jmoldx.2006.060012. PMC   1867615 . PMID   16931583.
  9. ↑ Peng, H.H., & Van den Veyyer, I.B. "HOW DOES ARRAY-BASED COMPARATIVE GENOMIC HYBRIDIZATION WORK?", 2008
  10. ↑ N/A, "Principles of DNA Sequencing" Archived 2013-04-04 at the Wayback Machine , 2013
  11. ↑ "What is Kleefstra syndrome?". Kleefstrasyndrome.org. Kleefstrasyndrome.org. Retrieved 3 February 2017.
  12. ↑ Kleefstra, Tjitske; Brunner, Han G.; Amiel, Jeanne; Oudakker, Astrid R.; Nillesen, Willy M.; Magee, Alex; Geneviève, David; Cormier-Daire, Valérie; van Esch, Hilde; Fryns, Jean-Pierre; Hamel, Ben C.J.; Sistermans, Erik A.; de Vries, Bert B.A.; van Bokhoven, Hans (August 2006). "Loss-of-Function Mutations in Euchromatin Histone Methyl Transferase 1 (EHMT1) Cause the 9q34 Subtelomeric Deletion Syndrome". The American Journal of Human Genetics. 79 (2): 370–377. doi:10.1086/505693. PMC   1559478 . PMID   16826528.
  13. ↑ Kleefstra, T; van Zelst-Stams, W A; Nillesen, W M; Cormier-Daire, V; Houge, G; Foulds, N; van Dooren, M; Willemsen, M H; Pfundt, R; Turner, A; Wilson, M; McGaughran, J; Rauch, A; Zenker, M; Adam, M P; Innes, M; Davies, C; Lopez, A G.-M.; Casalone, R; Weber, A; Brueton, L A; Navarro, A D.; Bralo, M P.; Venselaar, H; Stegmann, S P A; Yntema, H G; van Bokhoven, H; Brunner, H G (4 March 2009). "Further clinical and molecular delineation of the 9q subtelomeric deletion syndrome supports a major contribution of EHMT1 haploinsufficiency to the core phenotype". Journal of Medical Genetics. 46 (9): 598–606. doi:10.1136/jmg.2008.062950. PMC   3395372 . PMID   19372089.
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