chr12·hg38·133.3 Mb

Chromosome 12

A chromosome of developmental control and oncogenic power — home to the HOXC cluster that patterns the body, the KRAS oncogene that drives a quarter of all cancers, the keratin genes that armor epithelial surfaces, and NANOG that holds stem cells in their pluripotent state.

Physical Properties

Length133.3 Mb

Centromeresubmetacentric

p-arm34.8 Mb

q-arm96.1 Mb

GC content40.8%

Genomic Features

Protein-coding genes1,034

Gene density7.8 / Mb

CpG islands14,008

EPIC v2 probes47,668

Notable

Largest geneNELL2 (740 kb)

Disease associations

Phenylketonuria

Pancreatic cancer (KRAS)

Liposarcoma (MDM2)

· KRAS mutations drive ~25% of all human cancers

· MDM2 amplification is a hallmark of liposarcoma

· Contains the HOX C cluster at 12q13

Genomic Architecture

The 12q13 supercluster — A ~5 Mb region at 12q13 is one of the most gene-dense and functionally concentrated segments in the human genome, containing:

The HOXC gene cluster (~100 kb, 9 genes)

The type II keratin gene cluster (~780 kb, 26 genes)

Evolutionary History

Ancestral origin — Chromosome 12 derives from a double reciprocal rearrangement between two ancient acrocentric chromosomes containing material syntenic to modern chromosomes 12 and 22. This rearrangement occurred in the anthropoid line…

Deep conservation — Alignment with the chicken genome (>300 Myr divergence) identifies 13 segments covering ~72% of chromosome 12. The HOXC cluster is conserved across all bilaterians (>550 Myr), and the keratin gene cluster organization…

Deep Cuts

The most drugged oncogene's long road — KRAS was identified as an oncogene in 1982 and declared "undruggable" for nearly 40 years due to its picomolar GTP affinity and smooth surface. Sotorasib (AMG510), approved in 2021, was the first KRAS inhibitor — cova…

Naming NANOG — The gene was named by Austin Smith's lab after Tir na nOg, the Land of the Young in Celtic mythology — a realm where nobody ages. The name reflects NANOG's function in maintaining the "forever young" state of stem cel…

The orangutan centromere experiment — Chromosome 12 in orangutans provided the first definitive evidence that centromeres can reposition epigenetically. The orangutan centromere sits at a different position than in humans, with no underlying DNA sequence …

§ Deep dive

The 12q13 superclusterA ~5 Mb region at 12q13 is one of the most gene-dense and functionally concentrated segments in the human genome, containing:

The HOXC gene cluster (~100 kb, 9 genes)

The type II keratin gene cluster (~780 kb, 26 genes)

CDK4, CDK2, ERBB3, and other cell-cycle/signaling genes

VDR (vitamin D receptor)

This region is frequently amplified in sarcomas and is the core of the "12q13-15 amplicon"

Isochore structureBimodal — 12p is predominantly L1/L2 (GC-poor, gene-sparse), while 12q13 and distal 12q are H1/H2 (GC-rich, gene-dense). The compositional transition around the centromere is relatively abrupt

Segmental duplicationsPericentromeric region of 12p contains segmental duplications shared with multiple chromosomes; subtelomeric regions of both arms participate in the genome-wide exchange network

Common fragile sitesFRA12A (12q13.1) is a rare folate-sensitive fragile site associated with CGG repeat expansion

Repeat contentLINE density is elevated in the gene-poor 12p arm; Alu elements are enriched in the gene-dense 12q13 region, following the genome-wide pattern of Alu-GC correlation