Localization of the gene for human heart fatty acid binding protein to chromosome 1p32-1p33.

Heart fatty acid binding protein (hFABP) is an abundant 14-kDa cytosolic protein thought to be involved in trafficking of fatty acids from the plasma membrane to sites of beta-oxidation in mitochondria and peroxisomes and to the endoplasmic reticulum for lipid synthesis. A human hFABP cDNA isolated by polymerase chain reaction was used as a probe for in situ hybridization to metaphase chromosomes. A fragment of the gene for human hFABP was used as a probe for fluorescence in situ hybridization to metaphase chromosomes. The cDNA and genomic probes both localized the gene for human hFABP to chromosome 1p32-1p33.

Familial amyloidotic polyneuropathy: a new transthyretin position 30 mutation (alanine for valine) in a family of German descent.

Familial amyloidotic polyneuropathy (FAP) is a dominantly inherited form of amyloidosis usually associated with an abnormal transthyretin (TTR), previously known as prealbumin. Several disease-related variants of the protein, each with a different amino acid substitution and correlating DNA point mutation, have been identified. The TTR gene from a patient suffering from this disorder was asymmetrically amplified and directly sequenced, revealing a cytosine for thymine substitution in the second base of codon 30 and the creation of a novel Cfo I restriction endonuclease site in exon 2. This mutation results in a previously undescribed substitution of an alanine for valine in the final TTR protein. Analysis of the amino acid mutation reveals it to be a hydrophilic substitution at a hydrophobic core position. Alanine at position 30 represents the second FAP-associated mutation at position 30 in TTR.

Partial duplication of Xp: a case report and review of previously reported cases.

We report clinical and cytogenetic findings on a 24-year-old woman with short stature, irregular menses, and other anomalies suggestive of Ullrich-Turner syndrome (UTS). Chromosome analysis documented a de novo duplication of Xp21 without any apparent microscopic deletion. DNA studies showed that part of band Xp22.1 is also duplicated. The clinical findings are compared with 5 other patients with dup(Xp).

Proline at position 36: a new transthyretin mutation associated with familial amyloidotic polyneuropathy.

Familial amyloidotic polyneuropathy (FAP) is associated with the deposition of an abnormal transthyretin (TTR) molecule. We have studied DNA from a family of Greek descent with FAP. The proband's TTR gene was asymmetrically amplified by using PCR and then was sequenced directly, to reveal a cytosine-for-guanine substitution in codon 36. This substitution removes a recognition site for endonuclease Fnu4HI. Allele-specific PCR was employed for diagnosis of the mutation. The predicted amino acid change of alanine to proline at position 36 was confirmed by protein sequencing of the proband's plasma TTR.

Presymptomatic and prenatal diagnosis of myotonic muscular dystrophy with linked DNA probes.

Advances in neurogenetics are facilitating clinical care. Localization of the mutant gene that causes myotonic muscular dystrophy (DM) to chromosome 19 enabled our predictive testing using linked DNA probes in 74 members of 12 families at risk. Individuals sought either diagnostic confirmation or exclusion with childbearing in mind, or requested prenatal diagnosis. Valuable information was provided for 11 of 12 families. Of 14 individuals at 50% risk, 12 learned they did not have DM, two learned they did (although presymptomatic), and prenatal diagnoses of affected fetuses were made in three families--all with high degrees of certainty. The future opportunity for prenatal diagnosis was provided for 3 other families. The potential health risks to an affected female and her affected or nonaffected fetus provide cogent reasons for physicians to inform DM families in their care about these important advances and opportunities to avert grave complications.

Prenatal diagnosis of myotonic muscular dystrophy with linked deoxyribonucleic acid probes.

Since the localization of the myotonic muscular dystrophy gene, closer deoxyribonucleic acid markers have been discovered. These now facilitate both presymptomatic and prenatal diagnosis of myotonic muscular dystrophy. We report our prenatal diagnosis experience with six cases in five families. Obstetricians are advised to inform their patients with a family history of myotonic muscular dystrophy of these testing opportunities. The fetus of the mother with myotonic muscular dystrophy who remains in utero until term is at considerable risk, as is the mother herself, of serious obstetric complications.

A new transthyretin variant from a patient with familial amyloidotic polyneuropathy has asparagine substituted for histidine at position 90.

A new transthyretin variant which lost an Sph I cleavage site within exon 3 has been characterized. A 260 bp sequence containing exon 3 was amplified using the polymerase chain reaction, and the variant was found to possess a Bsm I cleavage site not present in normal transthyretin. This led to the conclusion that the histidine at position 90 was replaced by asparagine, and amino acid analysis supported the conclusion. The discovery of this mutation suggests that intermolecular binding between hydrophobic polypeptide loops on the surface of transthyretin can lead to familial amyloidotic polyneuropathy.

A new mutation causing familial amyloidotic polyneuropathy.

The DNA from an individual with familial amyloidotic polyneuropathy was examined. It did not possess any of the mutations which have previously been associated with familial amyloidotic polyneuropathy. However, a novel 7.0 kb Sph I restriction fragment was discovered, and the mutation creating it was localized to exon 3 of the transthyretin gene. This mutation was inherited from a parent, and may result in an amino acid substitution for glu89, his90 or ala91. The patient's transthyretin has a lower pI than normal transthyretin.

Prenatal diagnosis of Friedreich ataxia.

Friedreich ataxia is a progressive neurodegenerative disorder affecting the peripheral and central nervous systems. One in 50,000 of the population are affected by this recessively inherited disorder, with onset usually before puberty. The recent localization of the disease locus to chromosome 9 has made it possible to provide genetic counselling to families with at least one affected child. Tight linkage of the disease mutation to an anonymous DNA marker MCT112 (D9S15) has been shown with a pairwise lod score of 36.1 at 0 = 0. We report here the first prenatal diagnosis in Friedreich ataxia. Using MCT112 and the confidence interval approach, we have calculated risks for a fully informative family with one affected sib.

Localization of the genes for histatins to human chromosome 4q13 and tissue distribution of the mRNAs.

A cDNA coding for histatin 1 was isolated from a human submandibular-gland library and sequenced. This cDNA was used to probe RNAs isolated from a variety of tissues to investigate tissue-specific regulation and to determine whether histatins might play a role other than in the oral cavity. The same probe was also used for Southern blot analysis of human genomic DNA restricted with various enzymes, and it showed that the genes coding for histatins are on the same chromosome. In situ hybridization of the cDNA probe to metaphase chromosome spreads was performed to determine chromosomal location of the genes for histatins. A genomic fragment isolated using the cDNA probe was also hybridized to chromosome spreads, and the same chromosome was identified. The genes for histatins are located on chromosome 4, band q13. We have shown that three histatin mRNAs are expressed in human parotid and submandibular glands but in none of the other tissues studied. These results suggest that histatins are specific to salivary secretions.

Mapping the mutation causing the X-linked lymphoproliferative syndrome in relation to restriction fragment length polymorphisms on Xq.

The X-linked lymphoproliferative syndrome (XLP) results in fatal infectious mononucleosis, hypogamma-globulinemia, and malignant lymphoma. The mutation has been mapped relative to several restriction fragment length polymorphism (RFLP) markers in the Xq21-Xq27 vicinity. The DXS37 locus was found to be near both the DXS42 and XLP loci.

Linkage analysis of seven kindreds with the X-linked lymphoproliferative syndrome (XLP) confirms that the XLP locus is near DXS42 and DXS37.

Analysis of seven kindreds indicates that the XLP locus exhibits 1% recombination with DXS42 (lod = 17.5) and no recombination with DXS37 (lod = 13.3).

Chromosome deletion of Xq25 in an individual with X-linked lymphoproliferative disease.

High resolution chromosome analysis was done on lymphoblastoid cell lines, established during the past decade from affected males with X-linked lymphoproliferative disease (XLP) or from obligate female carriers, from 14 families. One cell line, from a male with XLP, has a partial deletion of band Xq25. The constitutional nature of the deletion is confirmed in chromosome studies of peripheral blood from the affected individual and represents the first such structural defect to be described in this disorder. Cell lines from the remaining 13 families do not have cytogenetically detectable deletions. This observation will facilitate precise localization, cloning and sequencing of the gene causing XLP.

Mapping the X-linked lymphoproliferative syndrome.

The X-linked lymphoproliferative syndrome is triggered by Epstein-Barr virus infection and results in fatal mononucleosis, immunodeficiency, and lymphoproliferative disorders. This study shows that the mutation responsible for X-linked lymphoproliferative syndrome is genetically linked to a restriction fragment length polymorphism detected with the DXS42 probe (from Xq24-q27). The most likely recombination frequency between the loci is 4%, and the associated logarithm of the odds is 5.26. Haplotype analysis using flanking restriction fragment length polymorphism markers indicates that the locus for X-linked lymphoproliferative syndrome is distal to probe DXS42 but proximal to probe DXS99 (from Xq26-q27). It is now possible to predict which members of a family with X-linked lymphoproliferative syndrome are carrier females and to diagnose the syndrome prenatally.