Human Genetics: A young patient with Proteus syndrome is pictured on page 292 of

Question

Human Genetics: A young patient with Proteus syndrome is pictured on page 292 of your textbook. Proteus Syndrome is caused by a mutation that constitutively activates AKT1, a serine/threonine kinase involved in cell growth and cell division. Why does Proteus Syndrome develop only through somatic mosaicism and not froma germline mutation? Please Answer in most detail as possible so I am able to understand.

Notes on Proteus Syndrome:

Proteus syndrome develops from dysregulated growth driven by a gain-of-function mutation in the AKTI gene. Somatic mosaicism involving the mutant AKT1/ Protein kinase B leads to disproportionate overgrowth of connective tissue including bone and vasculature. Patients appear normal at birth; abnormal growth patterns develop within 12 months.

Explanation / Answer

Somatic mosaicism is the occurrence of two genetically distinct populations of cells within an individual, derived from a postzygotic mutation.Mosaic mutations may be present in the germline or soma, although typically only mutations in the soma have phenotypic consequences or detectable by available genotyping methods. Mosaic mutations in germ cells are only discovered in the inherited conditions in multiple progeny. Mosaic mutations occur postzygotically and inherited by all subsequent cells in their lineage. Somatic errors in chromosomal segregation in early development induce a high rate of aneuploidy. In replication procedure, lagging strand leads to loss of genetic information at the ends of the chromosomes during every replication and in germline this problem is solved because the ends of chromosomes (telomeres) are protected by repetitive DNA which is synthesized by telomerase. Somatic mutations are thought to occur in all cells during replication. Mutations in microsatellites and other region of the genome cause the disease. Somatic mutations in AKT genes have cell-specific effects. The AKTs highlight the complex interaction of localized somatic mutation with tissue or cell-specific gene expression and signaling pathways.

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