6q27

Chromosome 6 long‑arm band q27 (6q27) refers to a distal region on human chromosome 6, situated beyond the centromere on the q arm. The region occupies roughly 3.5 megabases, with the 6q27 band demarcated cytogenetically by light staining and a few sub‑bands. Its sequence has been fully assembled in the GRCh38 reference genome.

The 6q27 locus contains several protein‑coding genes of clinical relevance. TCF7L2, a transcription factor involved in Wnt signaling, resides within this band and its polymorphisms are strongly linked to type 2 diabetes and coronary artery disease. Other notable genes include PPBP (pro‑platelet basic protein), which participates in platelet activation; COL5A2, encoding a component of type V collagen; and MIR1207‑5p, a microRNA implicated in tumor regulation. Several non‑coding RNAs and small nucleolar RNAs are also present, reflecting a complex regulatory landscape.

Clinical associations with 6q27 are diverse. Copy‑number alterations, both deletions and duplications, have been noted in various cancers, including colorectal carcinoma, where loss of one TCF7L2 allele can influence tumor behavior. Deletion of the distal 6q27 region has been reported in patients with developmental delay and congenital heart defects, suggesting dosage sensitivity of genes within this segment. Autosomal dominant inheritance patterns have emerged in familial cases of chromosomal instability linked to breakpoints within 6q27.

Cytogenetic studies reveal that 6q27 is a fragile site prone to rearrangements. Translocations involving this band can occur in lymphoid malignancies, often resulting in chimeric transcripts that disrupt gene regulation. Fluorescence in situ hybridization (FISH) probes specific to 6q27 are frequently used to detect submicroscopic deletions in patients with unexplained syndromic features.

Research into 6q27 continues to leverage high‑throughput sequencing, genome‑wide association studies, and functional genomics. Investigations focus on haplotype mapping of TCF7L2 variants, CRISPR‑mediated disruption of candidate genes, and chromatin conformation assays to elucidate regulatory interactions within this terminal chromosomal segment.