Camilla Heinzmann

Human monoamine oxidase A and B genes map to xp11.23 and are deleted in a patient with norrie disease

Monoamine oxidase A and B (MAO A and B) are the central enzymes that catalyze oxidative deamination of biogenic amines throughout the body. The regional locations of genes encoding MAO A and B on the X chromosome were determined by using full-length cDNA clones for human MAO A and B, respectively. Using somatic cell hybrids, in situ hybridization, and field-inversion gel electrophoresis as well as deletion mapping in a patient with Norrie disease, we concluded that these two genes are close to each other and to the DXS7 locus (Xp 11.3).

Assignment of a serotonin 5HT-2 receptor gene (HTR2) to human chromosome 13q14–q21 and mouse chromosome 14

A gene for serotonin 5HT-2 receptor (HTR2) is assigned to human chromosome 13 by somatic cell hybrids and to region 13q14-q21 by in situ hybridization. It is assigned to mouse chromosome 14 by somatic cell hybrid analysis.

Assignment of human 3-hydroxy-3-methylglutaryl coenzyme A reductase gene to q13 → q23 region of chromosome 5

We have used hamster cDNA probes for 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase (HMGCR) to determine the chromosomal location of the human gene for HMG CoA reductase. Southern blot analysis of genomic DNA from 16 independent mouse-human somatic cell hybrids showed that the human gene for HMG CoA reductase resides on chromosome 5. Analysis of Chinese hamster-human somatic cell hybrids selectively retaining human 5 or a portion of it showed that the gene locus for HMG CoA reductase can be assigned to the q13 → q23 region of chromosome 5.

Assignment of defensin gene(s) to human chromosome 8p23

A relatively abundant component of the polymorphonuclear leukocyte granulocytes has been recently isolated and called defensin. Defensins have antimicrobial activity against gram-positive and gram-negative bacteria and enveloped viruses. A cDNA insert for defensin HNP-1 (DEF1) has been used to map the gene(s) to human chromosome 8p23 using a mouse/human somatic cell hybrid panel and in situ hybridization to normal human metaphase chromosomes. Because of the similarity of HNP-1 defensin to other defensins, it is likely that two of these genes map to this region.

Chromosomal localization of the human vesicularamine transporter genes

The physiologic and behavioral effects of pharmacologic agents that interfere with the transport of monoamine neurotransmitters into vesicles suggest that vesicular amine transport may contribute to human neuropsychiatric disease. To determine whether an alteration in the genes that encode vesicular amine transport contributes to the inherited component of these disorders, we have isolated a human cDNA for the brain transporter and localized the human vesicular amine transporter genes. The human brain synaptic vesicle amine transporter (SVAT) shows unexpected conservation with rat SVAT in the regions that diverge extensively between rat SVAT and the rat adrenal chromaffin granule amine transporter (CGAT). Using the cloned sequences with a panel of mouse-human hybrids and in situ hybridization for regional localization, the adrenal CGAT gene (or VAT1) maps to human chromosome 8p21.3 and the brain SVAT gene (or VAT2) maps to chromosome 10q25. Both of these sites occur very close to if not within previously described deletions that produce severe but viable phenotypes.

Regulation of chicken apolipoprotein B: cloning, tissue distribution, and estrogen induction of mRNA.

Apolipoprotein (apo) B is a major protein component of plasma very low-density and low-density lipoproteins (VLDL and LDL, respectively) and serves as a recognition signal for the cellular binding and internalization of LDL by the apoB/E receptor. In contrast to the situation in mammals, avian apoB is also a component of specialized VLDL particles that are produced by the liver in response to estrogen. These particles transport cholesterol and triglyceride from the liver to the ovary for deposition in egg yolk. We report here the identification and characterization of cDNA clones for chicken apoB and their use in examining the tissue distribution and hormonal regulation of chicken apoB mRNA. The cDNA clones were identified by immunological screening of a phage lambda gt11 library constructed with hen liver mRNA and their identity was supported by sequence comparisons with mammalian apoB. The chicken apoB mRNA is approximately the same size as mammalian apoB mRNA (14 kb), and, as occurs in mammals, is present at high levels in liver and small intestine. Unlike mammals, the chicken apoB mRNA is also found at high levels in the kidney, consistent with previous protein biosynthetic studies. A DNA-excess solution-hybridization assay was used to quantitate apoB mRNA in these tissues and to examine its hormonal regulation. In control roosters the liver and kidney contained 65% and 10%, respectively, as much apoB mRNA as the small intestine. Within 24 h after estradiol administration, apoB mRNA was increased five- to seven-fold in liver but was unchanged in intestine and kidney. The increase in apoB mRNA content and the kinetics of induction parallel hepatic apoB synthesis, indicating that estrogen regulates apoB production through changes in the cellular abundance of apoB mRNA. The apoB mRNA increased rapidly following hormone treatment while the mRNA for another VLDL protein (apoII) showed a lag or slow phase of several hours before significant mRNA accumulation occurred. These data indicate that the liver can respond immediately to estrogen to increase apoB mRNA accumulation, while apoII mRNA accumulation appears to involve additional events or signals which occur slowly and are specific to this gene.

Complementary homeo protein gradients in developing limb buds.

A new human homeo box-containing gene designated Hox-5.2 was cloned and mapped to human chromosome 2. This homeo box is related in sequence to Abdominal-B, a Drosophila homeotic gene that specifies identity of posterior segments. An antibody probe was made using a human Hox-5.2 fusion protein and was found to stain posterior regions of mouse, chicken, and Xenopus embryos. Unexpectedly, when the distribution of Hox-5.2 antigen was compared with that of X1Hbox 1 antigen, a non-overlapping and mutually exclusive pattern was detected (e.g., in developing limb buds, intestine, and somites). Regions expressing Hox-5.2 do not express X1Hbox 1 protein, and vice versa. Hox-5.2 antigen is detected strongly in developing fore- and hindlimb buds, where it forms a gradient of nuclear protein throughout most of the mesenchyme. This gradient is maximal in distal and posterior regions. Hox-5.2 expression is activated in Xenopus limb regeneration blastemas, as expected for any gene involved in pattern formation. As described previously, a gradient of X1Hbox 1 protein can be detected in the forelimb. The latter gradient has the opposite polarity to that of Hox-5.2. i.e., maximal in anterior and proximal mesoderm. These two opposing gradients (and possibly others) could be involved in determining positional values in developing limb buds.

Assignment of the prealbumin (PALB) gene (familial amyloidotic polyneuropathy) to human chromosome region 18q11.2–q12.1

SummaryThe assignment of the human prealbumin (PALB) gene to chromosome region 18q11–q12.1 has been achieved using a human genomic probe in the study of human-mouse somatic cell hybrids and by in situ hybridization. Because familial amyloidotic polyneuropathy was reported previously to be due to a mutation in prealbumin, it can be inferred that the gene for this disorder also maps to 18q11.2–q12.1.

Assignment of the gene (RLBP1) for cellular retinaldehyde-binding protein (CRALBP) to human chromosome 15q26 and mouse chromosome 7

Cellular retinaldehyde-binding protein (CRALBP) has properties that suggest that it is involved in the visual process and, therefore, potentially with retinal diseases. A human cDNA probe has been used to map this gene to human chromosome 15q26 (somatic cell hybrids and in situ hybridization) and to mouse chromosome 7 by somatic cell hybrids.

Assignment of the myelin basic protein gene to human chromosome 18q22-qter

SummaryThe assignment of the human myelin basic protein gene to 18q22-qter has been made using a mouse cDNA probe in the study of human-mouse somatic cell hybrids and by in situ hybridization. These results confirm the earlier assignment using in situ studies alone by Saxe et al. (1985).