Notes

HUMAN PREMATURE AGING SYNDROMES
Some comparisons of the p53 and XPD mouse mutant phenotypes with those
of several segmental progeroid syndromes in humans are summarized in
Table 1. p53 ve xpd farelerinin mutant fenotipleri ile insanda bircok segmentte progeroid belirtilerle ilgili bazi karsilastirmalar tablo1 ve sayfa 53. te ozetlenmistir.

Two of the most well known human progeroid syndromes are
Hutchinson–Gilford syndrome (HGS), also referred to as progeria, and
Werner syndrome (WS).en cok bilinen insan progeroid turleri, HGS (ayni zamanda progeria), ve WS dir.

HGS patients appear normal at birth, but by the end of their second year growth begins to slow and loss of hair and subcutaneous fat begin (De Busk, 1972). Hgs hastalari normal olarak dunyaya gelirler fakat buyume caglarinda 2 yasin sonlarina dogru gelisme yavaslar, saclarda kayiplar olusmaya baslar ve cilt alti sismanlama baslar. (subkütan)

Although their intellectual development is normal, these children reach a height of only about 3 feet and a weight of about 35 pounds, and usually die of cardiovascular complications at an average age of 13 years. Zihinsel gelisim kapasiteleri normal olsa da, bu cocuklar en cok 3 feet ve yaklasik 35 pounds a kadar kilo alabilirler ve kardiyovaskuler rahatsızlıklar nedeniyle 13 yas civarinda olurler.

The syndrome is very rare (about 1 per 10 million births), and the genetic defect in HGS is not known, although it is usually assumed that HGS is due to an autosomal dominant mutation, possibly arising during germ cell production or development. Sendrom aslinda sıklıkla gorulmez, ancak 10 milyon dogumda 1 gibi olasiliga sahiptir ve hgs nin aslinda germ hucre uretimi ya da gelisimi sirasinda olusan otozomal dominant mutasyon nedeni ile olustugu dusunulse de aslinda hgs deki genetic hatanin nedeni bilinmemektedir.

The short stature and musculoskeletal abnormalities are more consistent with developmental abnormalities than premature aging, although fibroblasts taken from HGS
patients have short telomeres and little replicative potential remaining, suggesting the replicative life span of these cells may have been compromised by excessive apoptosis and cell replacement early in life.

The short stature and developmental abnormalities might then be due to insufficient cell
replacement from the various stem cell reservoirs with increasing age. Kisa boy ve gelisme anomalileri, yasla birlikte artan cesitli tipteki kok hucre rezervleri nedeniyle olusan yetersiz hucre degisimi nedeniyle olabilir.

However, other than short telomeres, there is no strong evidence for genetic
instability in HGS that might trigger such an early and continuing apoptotic
response. Yine de, kisa telomerden baska, hgs deki genetik yetersizligin erken ve suregen apoptotic cevabi tetikleyebilecegine dair guclu deliller mevcut degildir.

WS patients also appear normal at birth, and a diagnosis of WS is usually
not made until puberty, when growth begins to slow down (Martin and
Oshima, 2000). WS hastalari da aslinda dogumda bir anomali ile dunyaya gelmezler ve teshis ergenligin yavaslamaya basladigi doneme kadar genelde konulmaz.

This is followed by premature graying of hair, atrophy of various tissues (particularly reproductive tissues and skin), type 2 diabetes, atherosclerosis, and osteoporosis.
Most striking, however, is the genetic instability that accompanies WS, so WS patients are at high risk for neoplasia. Bunu, saclarin erken beyazlamasi, cesitli dokularda atrofi, tip 2 diabet, damar tikanikligi ve osteoporoz izler. Daha da carpicisi, ws ile iliskilendirilen genetik degiskenlik ve ws hastalari neoplazi acisindan yuksek risk altindadirlar.

This is consistent with the discovery that the WRN gene codes for a protein with
DNA helicase (known as a recQ helicase) and 3¢ Æ 5¢ exonuclease activities
(Gray et al., 1997; Huang et al., 1998). Bu, 3¢ Æ 5¢ cekirdek disi aktiviteleri ile birlikte dna helikazlari ile birlikte protein icin gerekli olan wrn gen kodlarinin kesfi ile tutarlidir.

Thus, this protein may be involved in any one or all of the following: replication, repair, recombination, and transcription. Fibroblasts isolated from WS patients have short life spans, but longer than that of HGS fibroblasts. Bu nedenle, bu protein bunlardan herhangibiri ya da hepsi ile iliskilidir: kopyalama, tamir, yeniden kombinasyon ve traskript. Fibroblasttan arindirilmis ws hastalarinin kisa bir yasami olmakla birlikte bu, hgs fibroblast hastalardan uzundur.

WS patients usually die of either cancer or myocardial infarction at a median age of about 47 to 48 years. Ws hastalari genelde kanser veya miyokard enfarktus nedeniyle ortalama 47-48 yaslarinda hayatlarini kaybederler.

In contrast to HGS and WS, patients with Bloom syndrome (BS) do not
appear normal at birth, but are born small, and remain smaller than normal
throughout their short life, with death usually occurring in their twenties
due to cancer. Hgs ve ws hastalarinin aksine, bs hastalari normal olarak dunyaya gelmezler; kucuk dogarlar, kisa yasamlari suresince gelismezler ve genelde 20 yas civarinda kanserden olurler.

The defective gene (BLM) associated with Bloom syndrome
also codes for an enzyme with a recQ-like DNA helicase activity, but not
exonuclease activity. Bloom sendromu ile iliskili yetersiz blm geni

Several speakers at the recent Keystone symposium on “DNA Helicases, Cancer and Aging” (March 12–17, 2002) suggested that the small stature of Bloom syndrome patients may result from excessive cell death, even in the fetal stage of life. Yakinlarda gerceklesen keystone “ dna helikazlari, kanser ve yaslanma” konulu sempozyumdaki bircok konusmaci bloom sendromunda gorulen kucuk yapinin/kisa boyun fetus halinde bile gorulen asiri hucre cogalmasi nedeni ile olabilecegine isaret ettiler.

Because BS is characterized by genomic instability, particularly sister chromatid exchanges, such cell death may be triggered by the accumulation of replication intermediates (Bischof et al.2001) that either induce cell death or lead to illegitimate recombination.

The growth defects associated with these three human syndromes appear not to be caused by growth hormone deficiency (Laron, 2002). Insanda gozlenen buyume ilgili bu uc sendromun aslinda buyume hormonu yetersizligi ile bir iliskisinin oldugunu soyleyemeyiz.


The preliminary results with Bloom syndrome raise the issue of whether excessive cell death also contributes to the phenotype of Werner, Hutchinson–Gilford, or Cockayne syndrome, all of which are characterized by short stature, and/or to other segmental progeroid syndromes. Bloom sendromu ile ilgili yapilmis olan daha onceki calismalara ait sonuclar, ayni zamanda tumu kisa boy ile karakterize edilen Werner, hutch.gilford ya da cockayne fenotipi ve/veya diger segmental progeroid sendromu ile iliskilendirlebilen yogun/Asiri hucre olumunun bu duruma bir etkisi olup olmadigi ile ilgili soru isaretlerini cogaltir.


On the other hand, the increased susceptibility to cancer might indicate that decreased apoptosis is occurring in WS patients (Campisi, 2002). Diger taraftan, kansere asiri duyarlilik ws hastalarinda olusan apoptozun azalabilecegine isaret edebilir.

These questions seem to deserve increased attention in future research on the roles of
cell death in aging and development of various aging phenotypes, and this may also tell us something about p53 function and aging, as Yang et al. (2002)
have reported that p53 may also play a role in regulating the activity of the
DNA helicases associated with Werner and Bloom syndromes. Bu sorulara, hucre olumlerinin yaslanma ve cesitli yaslanma fenotiplerinin gelisimi uzerindeki rolu ile ilgili ileride gerceklesebilecek arastirmalarda daha cok onem verilmelidir, ve bu ayrica p53 fonksiyonu ve yaslanma yaslanma bize yardimci olabilir. yang’in da (2002) belirttigi gibi, p53, werner ve bloom sendromu ile iliskili dna helikazlarinin aktivitesini duzenleyici rolu oynabilir.
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