Montgomery Robert K, Krasinski Stephen D, Hirschhorn Joel N, Grand Richard J
Division of Genetics, Department of Medicine, Program in Genomics, Children's Hospital, Boston, MA 02115, USA.
J Pediatr Gastroenterol Nutr. 2007 Dec;45 Suppl 2:S131-7. doi: 10.1097/MPG.0b013e31812e68f6.
Lactase-phlorizin hydrolase (LPH) is expressed only in the small intestine and is confined to absorptive enterocytes on the villi with a tightly controlled pattern of expression along the proximal to distal and crypt-villus axes of the intestine. LPH expression is regulated mainly at the level of lactase (LCT) gene transcription that directs 2 phenotypes: a decline in LCT activity (LCT nonpersistence) in mid-childhood in the majority of the world's population, and maintenance of the lactase levels found in infancy (LCT persistence) in people of northern European extraction and scattered populations elsewhere. The molecular mechanisms that regulate these phenotypes are not completely understood. A population genetic association of lactase persistence with 2 single nucleotide polymorphisms in the distal 5'-flanking region of LCT (-13.9T and -22A) has been confirmed in northern Europeans, but this fails to explain lactase persistence found in some African groups. Any hypothesis for the control of lactase expression must reconcile the presence of high levels of activity in early life in all humans and the characteristic loss of activity found subsequently in many but not all people.
乳糖酶-根皮苷水解酶（LPH）仅在小肠中表达，且局限于绒毛上的吸收性肠上皮细胞，其表达模式在肠道近端至远端以及隐窝-绒毛轴上受到严格控制。LPH的表达主要在乳糖酶（LCT）基因转录水平上进行调节，该基因有两种表型：世界上大多数人群在童年中期LCT活性下降（LCT非持续性），而北欧血统人群和其他地区散居人群则维持婴儿期的乳糖酶水平（LCT持续性）。调节这些表型的分子机制尚未完全明确。在北欧人群中已证实乳糖酶持续性与LCT基因5'侧翼远端区域的两个单核苷酸多态性（-13.9T和-22A）存在群体遗传关联，但这无法解释在一些非洲人群中发现的乳糖酶持续性现象。任何关于乳糖酶表达调控的假说都必须解释为何所有人类在生命早期都有高水平的活性，以及为何许多但并非所有人随后会出现特征性的活性丧失。
