Amniocytes, cultured

The GCMS analysis of methylcitrate or methylmalonate in the amniotic fluid is of advantage over enzyme analysis because of its rapidity. Moreover, it avoids possible maternal contamination of amniocyte cultures. In one documented instance the fetus was diagnosed as affected by methylcitrate analysis and normal by enzyme analysis an affected infant was born and the cells ultimately available for analysis were later shown to be maternal. In families in which the mutation is known, prenatal diagnosis may be carried out by analysis of DNA, but the numbers of mutations are such that this is not generally available. 

Prenatal and postnatal diagnoses can be made by enzyme assay of cultured amniocytes, fibroblasts or white blood cells. Treatment remains symptomatic. Sodium bicarbonate is necessary to correct the acidosis. Aspartic acid supplementation will improve the systemic condition but has no effect on the neurological disturbances. Biotin supplementation is of no value. 

Cultured fibroblasts or amniocytes can be probed with FAO substrates and carnitine. Cell cultures deficient of an FAO enzyme will accumulate specific acylcarni-tine species when incubated with substrates such as palmitate, allowing for the diagnosis of FAO disorders [28-37]. Modifications of this assay system have also been developed for the diagnosis of defects affecting the metabolism of branched-chain amino acids [20, 31, 34]. Recently, this approach was also adapted for the study of peripheral blood mononuclear cells [38]. 

Fibroblasts are typically grown from a small skin biopsy sample collected during an outpatient visit or as part of a planned surgical procedure following routine culturing techniques. Cell cultures may also be derived from umbilical cord or, for prenatal diagnostic purposes, from amniocytes obtained by amniocentesis. In our laboratory the analysis for each patient is performed in triplicate. 

Brown BI, Brown DH (1989) Branching enzyme activity of cultured amniocytes and chorionic villi prenatal testing for type IV glycogen storage disease. Am J Hum Genet 44 378-381... 

Biotinidase activity can be measured in cultured amniotic fluid cells and in amniotic fluid. Therefore, prenatal diagnosis of biotinidase deficiency is possible. Prenatal diagnosis has been performed in two at-risk pregnancies in which amniocentesis was performed because of advanced maternal age. The fetuses were found to be unaffected, and this was confirmed after birth. In addition to enzyme determination in amniocytes, a fetus was correctly shown to be a heterozygote by molecular mutation analysis in an at-risk pregnancy. Because treatment is so effective in this disorder, some laboratories are now performing prenatal diagnosis. 

Holocarboxylase synthetase deficiency can be diagnosed prenatally by assessing the response of carboxylase activity in cultured amniocytes (obtained by amniocentesis) to the addition of biotin, or by the detection of methylcitric and hydroxyisovaleric acids in the amniotic fluid. Prenatal therapy, by giving the mother 10 mg of biotin per day, results in sufficiently elevated fetal blood concentrations of biotin to prevent the development of organic acidemia at birth. 

Antenatal diagnosis for fetuses at risk for the urea cycle enzyme disorders can be made by appropriate enzyme assays and DNA analysis in the cultured amniocytes. 

The answer is a. (Murray, pp 259-267. Scriver, pp 3827-3876. Sack, pp 97—158. Wilson, pp 287-320.) Most enzymes are expressed in chorionic villi or amniocytes and allow prenatal diagnosis of metabolic disorders through cell culture and enzyme assay. Percutaneous umbilical blood sampling (PUBS), or cordocentesis, offers another strategy if the enzyme is normally present in leukocytes. However, transabdominal aspiration of the umbilical cord is difficult and must be performed later in pregnancy (18-1-weeks) than CVS (8 to 10 weeks). OC-fetoprotein (AFP) is not known to be involved in any metabolic disorders, but it is used as an index of fetal tissue differentiation and integrity. Amniotic or maternal serum OC-fetoprotein (MSAFP) is most often used to detect, respectively, neural tube defects or... 

For prenatal diagnosis, amniotic fluid can be used to identify acylcarni-tines characteristic of certain branched-chain amino acid disorders. Cultured amniocytes or chorionic villous cells can be used with in-vitro substrate loading for diagnosis of fatty acid and branched-chain amino acid disorders as described earlier for fibroblasts [13]. 

SUOX) chorionic villi cultured fibroblasts and amniocytes ... 

Sulfite oxidase deficiency Chorionic villi, amniotic fluid, cultured amniocytes I> II... 

MTHFR deficiency Chorionic villi, cultured amniocytes I, II... 

Argininemia I LPI HHH Fetal red cells Amniocytes/chorionic villi Amniocytes concentration should both be assayed Assay in cultured, not frozen sample... 

Glycerol kinase deficiency (17.hi, 17.1.2, and 17.1.3) Leukocytes, lymphoblastoid cells, fibroblasts, liver, kidney, small intestine, adrenal, cultured amniocytes Xp21 307030... 

Cell-free amniotic fluid and cultured amniocytes Iduronate 2-sulfatase... 

Cultured amniocytes N Acetylgalac tosam ine 6 - sulfatase (galactose 6-sulfatase)... 

Wilson disease Chorionic villi Cultured amniocytes DNA l-II... 

Sakuraba, H., Itoh, K., Kotani, M., Tai, T., Yamada, H., Kurosawa, K., Kuroki, Y., Suzuki, H., Utsunomiya, T., Inoue, H., and Suzuki, Y., 1993, Prenatal diagnosis of GM2-gangliosidosis Immunofluorescence analysis of GM2 in cultured amniocytes by confocal laser scanning microscopy, Brain Dev. 15 278-282. 

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