Ring chromosome

Chromosome whose ends have fused together to form a ring

Representative karyotype from a well differentiated transitional cell carcinoma of the bladder. The chromosome indicated by "mar" represents unidentified marker, "r" represents ring chromosome. Arrowheads indicate breakpoints. Also evident are monosomy 9, 18, and X and trisomy 7.

A ring chromosome is an aberrant chromosome whose ends have fused together to form a ring. Ring chromosomes were first discovered by Lilian Vaughan Morgan in 1926.[1] A ring chromosome is denoted by the symbol r in human genetics and R in Drosophila genetics. Ring chromosomes may form in cells following genetic damage by mutagens like radiation, but they may also arise spontaneously during development.

## Formation

[edit]

Formation of a ring chromosome.

In order for a chromosome to form a ring, both ends of the chromosome are usually missing, enabling the broken ends to fuse together. In rare cases, the telomeres at the ends of a chromosome fuse without any loss of genetic material, which results in a normal phenotype.[2]

Complex rearrangements, including segmental microdeletions and microduplications, have been seen in numerous ring chromosomes, providing important clues regarding the mechanisms of their formation.[3]

Small supernumerary rings can also form, resulting in a partial trisomy.[4]

Ring chromosomes are unstable during cell division and can form interlocking or fused rings.[4]

## Associated syndromes

[edit]

Human genetic disorders can be caused by ring chromosome formation. Although ring chromosomes are very rare, they have been found in all human chromosomes. Symptoms seen in patients carrying ring chromosomes are more likely to be caused by the deletion of genes in the telomeric regions of affected chromosomes, rather than by the formation of a ring structure itself.[5] Almost all ring chromosome syndromes feature marked growth delay.[4]

Ring chromosomes can be inherited or sporadic. Mosaicism is common and affects the severity of the condition.[5] Location of fusion also affects severity due to loss of differing amounts of genetic material from the ends of chromosomes.

Disorders arising from the formation of a ring chromosome include:

Chromosome  | Typical features  |

|
|

Ring chromosome 1 | Microcephaly, facial abnormalities  | [6]
Ring chromosome 2 | Small stature  | [7][8]
Ring chromosome 3 |  | [9]
Ring chromosome 4 | Craniofacial abnormalities | [10]
Ring chromosome 5 |  | [11]
Ring chromosome 6 | Microcephaly, facial abnormalities, hand abnormalities  | [12]
Ring chromosome 7 | Craniofacial abnormalities, speech deficits  | [13]
Ring chromosome 8 | Craniofacial abnormalities, hydronephrosis, hand abnormalities  | [14]
Ring chromosome 9 | Delayed growth, abnormal facial features, low muscle tone  | [15]
Ring chromosome 10 | Delayed growth, facial dysmorphism, reproductive abnormalities  | [16]
Ring chromosome 11 |  | [17]
Ring chromosome 12 | Delayed growth, abnormal facial features, microcephaly  | [18][19]
Ring chromosome 13 | Microcephaly, delayed growth, reproductive abnormalities  | [20]
Ring chromosome 14 | Epilepsy, intellectual disability  | [21]
Ring chromosome 15 | Growth delay, microcephaly, intellectual disability  | [22]
Ring chromosome 16 | Microcephaly, growth delay, facial abnormalities  | [23][24]
Ring chromosome 17 |  | [25]
Ring chromosome 18 | Growth delay, facial abnormalities  | [26]
Ring chromosome 19 |  | [27]
Ring chromosome 20 | Epilepsy, abnormal facial features, growth delay  | [28]
Ring chromosome 21 | Short stature, microcephaly, reproductive abnormalities  | [29]
Ring chromosome 22 | Hypotonia, autistic-like behavior  | [30]
Ring chromosome X | Turner syndrome |
Ring chromosome Y |  | [31]

## See also

[edit]

* Chromosome abnormalities

## References

[edit]

1. ^ Morgan, LV (Mar 1926). "Correlation between Shape and Behavior of a Chromosome". Proceedings of the National Academy of Sciences of the United States of America. 12 (3): 180–1\. Bibcode:1926PNAS...12..180M. doi:10.1073/pnas.12.3.180. PMC 1084483. PMID 16576974.
2. ^ Arnedo, Núria; Nogués, Carme; Bosch, Mercè; Templado, Cristina (2009-06-29). "Mitotic and meiotic behaviour of a naturally transmitted ring Y chromosome: reproductive risk evaluation -- Arnedo et al. 20 (2): 462 -- Human Reproduction". Human Reproduction. 20 (2): 462–468\. doi:10.1093/humrep/deh598. PMID 15528264. Archived from the original on 29 June 2009. Retrieved 2025-01-15.
3. ^ Shchelochkov, Oleg A.; Cooper, M Lance; Ou, Zhishuo; Peacock, Sandra; Yatsenko, Svetlana A.; Brown, Chester W.; Fang, Ping; Stankiewicz, Pawel; Cheung, Sau Wai (2008-07-25). "Mosaicism for r(X) and der(X)del(X)(p11.23)dup(X)(p11.21p11.22) provides insight into the possible mechanism of rearrangement". Molecular Cytogenetics. 1 (1): 16. doi:10.1186/1755-8166-1-16. ISSN 1755-8166. PMC 2518151. PMID 18655707.
4. ^ a b c Yip, Moh-Ying (2015). "Autosomal ring chromosomes in human genetic disorders". Translational Pediatrics. 4 (2): 164–174\. doi:10.3978/j.issn.2224-4336.2015.03.04. PMC 4729093. PMID 26835370.
5. ^ a b "ClinicalKey". www.clinicalkey.com. Retrieved 2025-01-15.
6. ^ "Ring chromosome 1 - Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". rarediseases.info.nih.gov. Archived from the original on 2022-02-03. Retrieved 2017-12-01.
7. ^ "Orphanet: Ring chromosome 2 syndrome". www.orpha.net.
8. ^ "Ring 2" (PDF). Archived from the original (PDF) on 2017-12-05. Retrieved 2017-12-04.
9. ^ "Orphanet: Ring chromosome 3 syndrome". www.orpha.net.
10. ^ "Orphanet: Ring chromosome 4 syndrome". www.orpha.net.
11. ^ "Orphanet: Ring chromosome 5 syndrome". www.orpha.net.
12. ^ "Orphanet: Ring chromosome 6 syndrome". www.orpha.net.
13. ^ "Orphanet: Ring chromosome 7 syndrome". www.orpha.net.
14. ^ "Ring chromosome 8 - Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". rarediseases.info.nih.gov.
15. ^ "Ring 9" (PDF). Archived from the original (PDF) on 2016-04-18. Retrieved 2017-12-04.
16. ^ "Orphanet: Ring chromosome 10 syndrome". www.orpha.net.
17. ^ "Ring chromosome 11 - Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". rarediseases.info.nih.gov. Archived from the original on 2022-02-03. Retrieved 2017-12-01.
18. ^ "Orphanet: Ring chromosome 12 syndrome". www.orpha.net.
19. ^ "Ring chromosome 12 | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". rarediseases.info.nih.gov. Archived from the original on 2022-02-03. Retrieved 2017-12-04.
20. ^ "Ring chromosome 13 | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". rarediseases.info.nih.gov. Retrieved 2017-12-04.
21. ^ "Orphanet: Ring chromosome 13 syndrome". www.orpha.net.
22. ^ "Ring 15" (PDF). Archived from the original (PDF) on 2017-12-05. Retrieved 2017-12-04.
23. ^ "Orphanet: Ring chromosome 16 syndrome". www.orpha.net.
24. ^ "Ring chromosome 16 | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". rarediseases.info.nih.gov. Retrieved 2017-12-04.
25. ^ "Orphanet: Ring chromosome 17 syndrome". www.orpha.net.
26. ^ "Orphanet: Ring chromosome 18 syndrome". www.orpha.net.
27. ^ "Orphanet: Ring chromosome 19 syndrome". www.orpha.net.
28. ^ "Ring chromosome 20 | Genetic and Rare Diseases Information Center (GARD) – an NCATS Program". rarediseases.info.nih.gov. Retrieved 2017-12-04.
29. ^ "Orphanet: Ring chromosome 21 syndrome". www.orpha.net.
30. ^ "Orphanet: Ring chromosome 22 syndrome". www.orpha.net.
31. ^ "Orphanet: Ring chromosome Y syndrome". www.orpha.net.

## External links

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* Atlas of Genetics and Cytogenetics in Oncology and Haematology Archived 2007-08-24 at the Wayback Machine, explains HOW the ring formation causes abnormalities.

* v
* t
* e

Chromosome abnormalities

Autosomal|

| Duplications,
including trisomies|

* 1q21.1 duplication syndrome
* 2q31.1 microduplication
* Trisomy 8
* Trisomy 9
* Tetrasomy 9p
* Distal trisomy 10q
* Patau syndrome
* 13
* Trisomy 16
* 16p11.2 duplication syndrome
* Trisomy 18
* Down syndrome
* 21
* 22q11.2 duplication syndrome
* Trisomy 22
* Cat-eye syndrome
* 22

|

Deletions|

* (1q21.1 copy number variations/1q21.1 deletion syndrome/1q21.1 duplication syndrome/TAR syndrome/1p36 deletion syndrome)
* 1
* Wolf–Hirschhorn syndrome
* 4
* Cri du chat syndrome/Chromosome 5q deletion syndrome
* 5
* Williams syndrome
* 7
* Jacobsen syndrome
* 11
* Miller–Dieker syndrome/Smith–Magenis syndrome/17q12 microdeletion syndrome
* 17
* DiGeorge syndrome
* 22
* 22q11.2 distal deletion syndrome
* 22
* 22q13 deletion syndrome
* 22

* genomic imprinting
* Angelman syndrome/Prader–Willi syndrome (15)

* Distal 18q-/Proximal 18q-

X/Y linked|

| Monosomies|

* Turner syndrome (45,X)

|

Trisomies/tetrasomies,
other karyotypes/mosaics|

* Klinefelter syndrome (47,XXY)
* XXYY syndrome (48,XXYY)
* XXXY syndrome (48,XXXY)
* XXXYY syndrome (49,XXXYY)
* XXXXY syndrome (49,XXXXY)

* Trisomy X (47,XXX)
* Tetrasomy X (48,XXXX)
* Pentasomy X (49,XXXXX)

* XYY syndrome (47,XYY)
* XYYY syndrome (48,XYYY)
* XYYYY syndrome (49,XYYYY)

* 45,X/46,XY
* 46,XX/46,XY

Translocations|

| Leukemia/lymphoma|

| Lymphoid|

* Burkitt lymphoma t(8 MYC;14 IGH)
* Follicular lymphoma t(14 IGH;18 BCL2)
* Mantle cell lymphoma/Multiple myeloma t(11 CCND1:14 IGH)
* Anaplastic large-cell lymphoma  t(2 ALK;5 NPM1)
* Acute lymphoblastic leukemia

|

Myeloid|

* Philadelphia chromosome t(9 ABL; 22 BCR)
* Acute myeloblastic leukemia with maturation t(8 RUNX1T1;21 RUNX1)
* Acute promyelocytic leukemia t(15 PML,17 RARA)
* Acute megakaryoblastic leukemia t(1 RBM15;22 MKL1)

Other|

* Ewing sarcoma t(11 FLI1; 22 EWS)
* Synovial sarcoma t(x SYT;18 SSX)
* Dermatofibrosarcoma protuberans t(17 COL1A1;22 PDGFB)
* Myxoid liposarcoma t(12 DDIT3; 16 FUS)
* Desmoplastic small-round-cell tumor t(11 WT1; 22 EWS)
* Alveolar rhabdomyosarcoma t(2 PAX3; 13 FOXO1) t (1 PAX7; 13 FOXO1)

Other|

* Fragile X syndrome
* Uniparental disomy
* XX male syndrome/46,XX testicular disorders of sex development
* Marker chromosome
* Ring chromosome
* 6; 9; 14; 15; 18; 20; 21, 22

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