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FB2026_01
,
released March 12, 2026
This report describes galactose epimerase deficiency, which is a subtype of galactosemia. Galactose epimerase deficiency is inherited as an autosomal recessive. The human gene implicated in this disease is UDP-Galactose-4-Epimerase (GALE), which encodes an enzyme in the galactose metabolic pathway. There is a single fly ortholog, Dmel\Gale, for which classical loss-of-function alleles, RNAi-targeting constructs, and alleles caused by insertional mutagenesis have been generated.
A UAS construct driving the wild-type human gene, Hsap\GALE, has been introduced into flies. Heterologous rescue (functional complementation) of the lethal phenotype of Dmel\Gale loss-of-function mutations has been demonstrated (FBrf0211672).
Loss-of-function alleles of Dmel\Gale are lethal on the food typically used for Drosophila culture. Animals with partial loss of Gale function survive in the absence of galactose, but not if exposed to dietary galactose; this recapitulates a key aspect of the human disease. Physical interactions of the Dmel\Gale protein product have been described; see below and in the FlyBase gene report for Dmel\Gale.
[updated Jun. 2017 by FlyBase; FBrf0222196]
Classic galactosemia (type I) is the most severe and the most common form of the condition, occurring in 1 in 30,000-60,000 newborns. If infants with classic galactosemia are not treated promptly with a low-galactose diet, life-threatening complications appear within a few days after birth. Affected infants typically develop feeding difficulties, lethargy, failure to thrive, jaundice, liver damage, and abnormal bleeding. Galactosemia type II and type III are less common and are typically less severe. [from Genetics Home Reference, Galactosemia; 2016.01.25]
Galactosemias are disorders of galactose metabolism. Symptoms vary, depending upon the enzyme affected. [from MIM:230400, MIM:230200. MIM:230350, MIM:618881; 2020.07.13]
[GALACTOSEMIA III; GALAC3](https://omim.org/entry/230350)
[UDP-GALACTOSE-4-EPIMERASE; GALE](https://omim.org/entry/606953)
Symptoms of galactose epimerase deficiency vary from mild to severe. In milder forms the enzyme deficiency appears to be restricted to specific tissues or cell-types, for example, to circulating red and white blood cells. More severe forms that affect additional tissues are described as 'generalized' galactose epimerase deficiency and have symptoms of classical galactosemia, including jaundice, vomiting, hypotonia, failure to thrive, and enlarged liver. Long-term complications may include motor and intellectual delays and cataracts. [from MIM:230350; 2016.01.26]
Galactose epimerase deficiency is inherited as an autosomal recessive; it is caused by homozygous or compound heterozygous mutation in the UDP-galactose-4-epimerase gene (GALE). [from MIM:230350; 2016.01.26]
UDP-galactose-4-prime-epimerase catalyzes the interconversion of UDP-galactose and UDP-glucose. [from MIM:606953; 2016.01.26]
One to one: 1 human to 1 Drosophila.