A bitter pill to swallow.

Foreign body aspiration can be a life-threatening emergency requiring immediate intervention. However, unlike in children, clinical presentation of foreign bodies in adults often varies with regard to symptoms and signs and occurs without asphyxia. We here describe the case of a 65-year-old man on maintenance hemodialysis who developed dyspnea and left chest aspiration pneumonia after swallowing one tablet of the phosphate binder sevelamer. This case illustrates that elderly patients with swallowing complaints should be taken serious when they complain about their subsequent frustration of ingestion of their pills.

SMPDL3b modulates insulin receptor signaling in diabetic kidney disease.

Sphingomyelin phosphodiesterase acid-like 3b (SMPDL3b) is a lipid raft enzyme that regulates plasma membrane (PM) fluidity. Here we report that SMPDL3b excess, as observed in podocytes in diabetic kidney disease (DKD), impairs insulin receptor isoform B-dependent pro-survival insulin signaling by interfering with insulin receptor isoforms binding to caveolin-1 in the PM. SMPDL3b excess affects the production of active sphingolipids resulting in decreased ceramide-1-phosphate (C1P) content as observed in human podocytes in vitro and in kidney cortexes of diabetic db/db mice in vivo. Podocyte-specific Smpdl3b deficiency in db/db mice is sufficient to restore kidney cortex C1P content and to protect from DKD. Exogenous administration of C1P restores IR signaling in vitro and prevents established DKD progression in vivo. Taken together, we identify SMPDL3b as a modulator of insulin signaling and demonstrate that supplementation with exogenous C1P may represent a lipid therapeutic strategy to treat diabetic complications such as DKD.

Identification of new translocation breakpoints at 12q13 in lipomas.

Cytogenetic studies of banded chromosomes and fluorescence in situ hybridization (FISH) of several yeast artificial chromosomes (YACs) that are part of a 128-kb resolution physical map of a portion of 12q13 revealed that 4/14 (28%) lipomas have breakpoints in 12q13. These breakpoints are more than 10 Mb away from the HMGIC gene at 12q14-q15, which is known to be modified in some lipomas. FISH with individual YACs at 12q13 enabled us to identify four YACs that span three breakpoints. Our results suggest that genes other than HMGIC on human chromosome 12 may be involved in the etiology of lipoma development.

Disseminated tuberculosis after renal transplantation. A report of two cases.

Disseminated mycobacterial infections occurred in two female renal graft recipients late after transplantation. In the first patient, initially presenting with fever, diagnosis was made at autopsy. Temporary defervescence following antibiotic therapy with ofloxacin possibly contributed to the fatal diagnostic delay. In the second case, body temperature was normal throughout the protracted course of the patient's illness. Her presenting symptom was rapidly increasing ascites, attributed initially to chronic liver disease. These cases demonstrate that tuberculosis remains a serious complication after renal transplantation, in particular due to its sometimes atypical clinical manifestations. Response to antibacterial therapy has to be critically evaluated in order to avoid fatal diagnostic delay.

Cloning, chromosomal localization, and physical linkage of the beta and gamma subunits (SCNN1B and SCNN1G) of the human epithelial amiloride-sensitive sodium channel.

Three subunits of the amiloride-sensitive Na+ channel, named alpha, beta, and gamma, have previously been cloned in rat colon. The human lung alpha chain (SCNN1A) has also been cloned and its gene localized on chromosome 12p13. We now report the molecular cloning of the human lung beta (SCNN1B) and gamma (SCNN1G) chains. In situ hybridization and pulsed-field electrophoresis experiments demonstrate that both genes are located within a common 400-kb fragment on chromosome 16p12-p13. Screening of the cDNA library reveals two forms of the beta subunit that differ by the presence or absence of a 464-bp fragment in the 3' region. A frameshift in the short form modifies the COOH terminal sequence of the corresponding protein. Since several similar frameshifts mutations have recently been reported in patients affected by a rare form of hypertension, the existence of COOH truncated forms of the beta chain might be of physiological importance.

Is the rise in plasma beta-2-microglobulin seen during hemodialysis meaningful?

Beta 2-Microglobulin (beta 2M) plasma levels and levels of a second low-molecular-weight protein (myoglobin) were studied during a 2- to 4-hour sham dialysis period (no dialysate flow, no weight loss) and during a 4- to 5-hour hemodialysis (HD) with a Cuprophan capillary dialyzer. While no rise of the beta 2M or myoglobin levels occurred during sham dialysis, a rise of 22.1 +/- (SD) 8.5% (beta 2M) or 19.9 +/- 12.1% (myoglobin) was seen during regular HD. The increases of both molecules showed a significant correlation (r = 0.44; p less than 0.03). Both rises could not be completely abolished using correction factors for hemoconcentration. The rises occurred irrespectively of the dialysate buffer. The results suggest that neither the Cuprophan membrane nor the extracorporeal circuit were responsible for the rise of both molecules during HD. It seems more likely that changes of the extracellular volume and extra- to intracellular water shifts are involved and account for the majority of the rise. However, the possibility of minor increase in the extracellular mass of beta 2M or myoglobin cannot be excluded completely.

Mapping of the 12q12-q22 region with respect to tumor translocation breakpoints.

The consistent involvement of the region 12q13-q15 in numerous human tumors speaks in favor of the presence of genes that may contribute to oncogenesis. Mapping genes within this region of chromosome 12 is a necessary step toward the identification of those that play a role in this process. We have undertaken a multiplex analysis using translocation breakpoint mapping to order from the centromere to the telomere a series of 24 loci from the region 12q12-q22. Thirteen adipose tissue tumors with seven different chromosome changes involving the long arm of chromosome 12 (12q) were used. Since most of these loci are genes or anonymous DNA segments largely available to the scientific community, this map should be useful for investigation of genetic disorders associated with chromosome 12q. While these breakpoints were used as natural landmarks to order groups of loci, this work has positioned them more accurately, leading to a better chromosomal definition of the translocations than the one derived from standard cytogenetic studies.

A 5.5-Mb high-resolution integrated map of distal 11q13.

The distal part of 11q13, which contains several genes relevant to human diseases, has been poorly mapped as part of genome-wide mapping efforts. In the prospect of drawing a fine-scale integrated map of the area containing KRN1 and OMP, we have established a framework of markers by hybridization to DNA of somatic cell hybrids and by fluorescence in situ hybridization (FISH) on metaphase chromosomes. The probes studied were used to isolate 27 YACs and 16 cosmids that could be organized in three contigs covering approximately 6 Mb. These contigs were separated by two gaps that are likely to contain sequences underrepresented in YAC libraries. They were then integrated based on long-range restriction mapping and DNA-fiber FISH into a high-resolution physical map, which covers a 5.5-Mb region and includes 36 anonymous markers and 10 genes. This map will be used to search for genes within the 2/3 of this region where none have been localized as yet. It will also lay the ground for the characterization of an amplicon surrounding GARP in breast cancer and for the search of disease genes within this region.

Normal cardiovascular development in mice deficient for 16 genes in 550 kb of the velocardiofacial/DiGeorge syndrome region.

Hemizygous interstitial deletions in human chromosome 22q11 are associated with velocardiofacial syndrome and DiGeorge syndrome and lead to multiple congenital abnormalities, including cardiovascular defects. The gene(s) responsible for these disorders is thought to reside in a 1.5-Mb region of 22q11 in which 27 genes have been identified. We have used Cre-mediated recombination of LoxP sites in embryonic stem cells and mice to generate a 550-kb deletion encompassing 16 of these genes in the corresponding region on mouse chromosome 16. Mice heterozygous for this deletion are normal and do not exhibit cardiovascular abnormalities. Because mice with a larger deletion on mouse chromosome 16 do have heart defects, the results allow us to exclude these 16 genes as being solely, or in combination among themselves, responsible for the cardiovascular abnormalities in velocardiofacial/DiGeorge syndrome. We also generated mice with a duplication of the 16 genes that may help dissect the genetic basis of "cat eye" and derivative 22 syndromes that are characterized by extra copies of portions of 22q11, including these 16 genes. We also describe a strategy for selecting cell lines with defined chromosomal rearrangements. The method is based on reconstitution of a dominant selection marker after Cre-mediated recombination of LoxP sites. Therefore it should be widely applicable to many cell lines.

Der(22) syndrome and velo-cardio-facial syndrome/DiGeorge syndrome share a 1.5-Mb region of overlap on chromosome 22q11.

Derivative 22 (der[22]) syndrome is a rare disorder associated with multiple congenital anomalies, including profound mental retardation, preauricular skin tags or pits, and conotruncal heart defects. It can occur in offspring of carriers of the constitutional t(11;22)(q23;q11) translocation, owing to a 3:1 meiotic malsegregation event resulting in partial trisomy of chromosomes 11 and 22. The trisomic region on chromosome 22 overlaps the region hemizygously deleted in another congenital anomaly disorder, velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS). Most patients with VCFS/DGS have a similar 3-Mb deletion, whereas some have a nested distal deletion endpoint resulting in a 1.5-Mb deletion, and a few rare patients have unique deletions. To define the interval on 22q11 containing the t(11;22) breakpoint, haplotype analysis and FISH mapping were performed for five patients with der(22) syndrome. Analysis of all the patients was consistent with 3:1 meiotic malsegregation in the t(11;22) carrier parent. FISH-mapping studies showed that the t(11;22) breakpoint occurred in the same interval as the 1.5-Mb distal deletion breakpoint for VCFS. The deletion breakpoint of one VCFS patient with an unbalanced t(18;22) translocation also occurred in the same region. Hamster-human somatic hybrid cell lines from a patient with der(22) syndrome and a patient with VCFS showed that the breakpoints occurred in an interval containing low-copy repeats, distal to RANBP1 and proximal to ZNF74. The presence of low-copy repetitive sequences may confer susceptibility to chromosome rearrangements. A 1.5-Mb region of overlap on 22q11 in both syndromes suggests the presence of dosage-dependent genes in this interval.

Detailed map of a region commonly amplified at 11q13-->q14 in human breast carcinoma.

Amplification of loci present on band q13 of human chromosome 11 is a feature of a subset of estrogen receptor positive breast carcinomas prone to metastasis. As many as five distinct amplification units have been described on 11q13. They include particularly a genomic area encompassing the GARP gene at 11q13.5-->q14.1. We have reassessed our current knowledge of this region, located telomeric to CCND1 and EMS1, which is amplified in 7-10% of mammary tumors. The loose definition of the driving forces of these amplification events led us to map accurately the boundaries of the amplifiable region, and thus to contribute a physical and transcriptional map of a 3-Mb region of chromosome 11. Four new genes were placed on the regional map, namely CBP2, CLNS1A, UVRAG, and PAK1. We have narrowed the core of the 11q13-->q14 amplicon to a 350-kb area encompassing D11S533, mostly on its telomeric side. The map reported here represents an indispensable step toward sequencing the entire region, and thus toward uncovering gene(s) which play(s) a critical role in breast cancer progression.

TBX1 is responsible for cardiovascular defects in velo-cardio-facial/DiGeorge syndrome.

Velo-cardio-facial syndrome (VCFS)/DiGeorge syndrome (DGS) is a human disorder characterized by a number of phenotypic features including cardiovascular defects. Most VCFS/DGS patients are hemizygous for a 1.5-3.0 Mb region of 22q11. To investigate the etiology of this disorder, we used a cre-loxP strategy to generate mice that are hemizygous for a 1.5 Mb deletion corresponding to that on 22q11. These mice exhibit significant perinatal lethality and have conotruncal and parathyroid defects. The conotruncal defects can be partially rescued by a human BAC containing the TBX1 gene. Mice heterozygous for a null mutation in Tbx1 develop conotruncal defects. These results together with the expression patterns of Tbx1 suggest a major role for this gene in the molecular etiology of VCFS/DGS.