Interphase nucleolar organizer region distribution in the tissues of oral leukoplakia, oral submucous fibrosis and oral cancer

Abstract Background DNA tandem repeats (TRs) are often abundant and occupy discrete regions in eukaryotic genomes. These TRs often cause or generate chromosomal rearrangements, which, in turn, drive chromosome evolution and speciation. Tracing the chromosomal distribution of TRs could therefore provide insights into the chromosome dynamics and speciation among closely related taxa. The basic chromosome number in the genus Senna is 2n = 28, but dysploid species like Senna tora have also been observed. Objective To understand the dynamics of these TRs and their impact on S. tora dysploidization. Methods We performed a comparative fluorescence in situ hybridization (FISH) analysis among nine closely related Senna species and compared the chromosomal distribution of these repeats from a cytotaxonomic perspective by using the ITS1-5.8S-ITS2 sequence to infer phylogenetic relationships. Results Of the nine S. tora TRs, two did not show any FISH signal whereas seven TRs showed similar and contrasting patterns to other Senna species. StoTR01_86, which was localized in the pericentromeric regions in all S. tora, but not at the nucleolar organizer region (NOR) site, was colocalized at the NOR site in all species except in S. siamea. StoTR02_7_tel was mostly localized at chromosome termini, but some species had an interstitial telomeric repeat in a few chromosomes. StoTR05_180 was distributed in the subtelomeric region in most species and was highly amplified in the pericentromeric region in some species. StoTR06_159 was either absent or colocalized in the NOR site in some species, and StoIGS_463, which was localized at the NOR site in S. tora, was either absent or localized at the subtelomeric or pericentromeric regions in other species. Conclusions These data suggest that TRs play important roles in S. tora dysploidy and suggest the involvement of 45S rDNA intergenic spacers in “carrying” repeats during genome reshuffling.

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The genomic structure of a human chromosome 22 nucleolar organizer region determined by TAR cloning

Scientific Reports ◽

10.1038/s41598-021-82565-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Jung-Hyun Kim ◽

Vladimir N. Noskov ◽

Aleksey Y. Ogurtsov ◽

Ramaiah Nagaraja ◽

Nikolai Petrov ◽

...

Keyword(s):

Genomic Structure ◽

Organizer Region ◽

Nucleolar Organizer Region ◽

Nucleolar Organizer ◽

Chromosome 21 ◽

Reference Sequence ◽

Chromosome 22 ◽

Rdna Variation ◽

High Level ◽

Tar Cloning

AbstractThe rDNA clusters and flanking sequences on human chromosomes 13, 14, 15, 21 and 22 represent large gaps in the current genomic assembly. The organization and the degree of divergence of the human rDNA units within an individual nucleolar organizer region (NOR) are only partially known. To address this lacuna, we previously applied transformation-associated recombination (TAR) cloning to isolate individual rDNA units from chromosome 21. That approach revealed an unexpectedly high level of heterogeneity in human rDNA, raising the possibility of corresponding variations in ribosome dynamics. We have now applied the same strategy to analyze an entire rDNA array end-to-end from a copy of chromosome 22. Sequencing of TAR isolates provided the entire NOR sequence, including proximal and distal junctions that may be involved in nucleolar function. Comparison of the newly sequenced rDNAs to reference sequence for chromosomes 22 and 21 revealed variants that are shared in human rDNA in individuals from different ethnic groups, many of them at high frequency. Analysis infers comparable intra- and inter-individual divergence of rDNA units on the same and different chromosomes, supporting the concerted evolution of rDNA units. The results provide a route to investigate further the role of rDNA variation in nucleolar formation and in the empirical associations of nucleoli with pathology.

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Mandibular Canal Widening and Bell’s Palsy: Sequelae of Perineural Invasion in Oral Cancer

Case Reports in Dentistry ◽

10.1155/2016/3010934 ◽

2016 ◽

Vol 2016 ◽

pp. 1-4

Author(s):

Gopinath Thilak Parepady Sundar ◽

Vishwanath Sherigar ◽

Sameep S. Shetty ◽

Shree Satya ◽

Sourabh M. Gohil

Keyword(s):

Oral Cancer ◽

Perineural Invasion ◽

Oral Submucous Fibrosis ◽

Inferior Alveolar Nerve ◽

Mandibular Canal ◽

Distinct Disease ◽

Nerve Tracts ◽

Submucous Fibrosis ◽

Neurological Disturbance ◽

Shed Light

Perineural invasion is an underrecognized route of metastatic spread along the nerve bundles within the nerve sheath into the surrounding tissues. It hinders the ability to establish local control as tumour cells can traverse along nerve tracts well beyond the extent of any local invasion rendering them inoperable and unresectable. Perineural invasion is a marker of poor prognosis. Oral submucous fibrosis with oral cancer constitutes a clinicopathologically distinct disease. Our case highlights an enigmatic presentation of oral submucous fibrosis and its coexistence with oral cancer presenting with unusual neurological disturbance of the inferior alveolar nerve and facial nerve and diffuse widening of the mandibular canal. The objective of this case report is to enumerate the significance of perineural invasion in determining the course of the disease and necessitate the need for future studies that can shed light on molecular mediators and pathogenesis of perineural spread.

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