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Progeroid syndromes (PS) are a group of rare genetic disorders that mimic physiological aging, making affected individuals appear to be older than they are. The term ''progeroid syndrome'' does not necessarily imply progeria (Hutchinson-Gilford progeria syndrome), which is a specific type of progeroid syndrome. ''Progeroid'' means "resembling premature aging", a definition that can apply to a broad range of diseases. Familial Alzheimer's disease and familial Parkinson's disease are two well-known accelerated-aging diseases that are more frequent in older individuals. They affect only one tissue and can be classified as unimodal progeroid syndromes. Segmental progeria, which is more frequently associated with the term ''progeroid syndrome'', tends to affect multiple or all tissues while causing affected individuals to exhibit only some of the features associated with aging. All disorders within this group are thought to be monogenic, meaning they arise from mutations of a single gene. Most known PS are due to genetic mutations that lead to either defects in the DNA repair mechanism or defects in lamin A/C. Examples of PS include Werner syndrome (WS), Bloom syndrome (BS), Rothmund–Thomson syndrome (RTS), Cockayne syndrome (CS), xeroderma pigmentosum (XP), trichothiodystrophy (TTD), combined xeroderma pigmentosum-Cockayne syndrome (XP-CS), restrictive dermopathy (RD), and Hutchinson-Gilford progeria syndrome (HGPS). Individuals with these disorders tend to have a reduced lifespan.〔 Progeroid syndromes have been widely studied in the fields of aging, regeneration, stem cells, and cancer. The most widely studied of the progeroid syndromes are Werner syndrome and Hutchinson-Gilford progeria, as they are seen to most resemble natural aging.〔 ==Defects in DNA repair== One of the main causes of progeroid syndromes is genetic mutations, which lead to defects in the cellular processes that repairs DNA. The DNA damage theory of aging proposes that aging is a consequence of the accumulation of naturally occurring DNA damages. The accumulated damage may arise from reactive oxygen species (ROS), chemical reactions (e.g. with intercalating agents), radiation, depurination, and deamination. Mutations in three classes of DNA repair proteins, RecQ protein-like helicases (RECQLs), nucleotide excision repair (NER) proteins, and nuclear envelope proteins LMNA (lamins) have been associated with the following progeroid syndromes: *Werner syndrome (WS) *Bloom syndrome (BS) *Rothmund–Thomson syndrome (RTS) *Cockayne syndrome (CS) *Xeroderma pigmentosum (XP) *Trichothiodystrophy (TTD) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Progeroid syndromes」の詳細全文を読む スポンサード リンク
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