Doublecortin is a developmentally regulated, microtubule-associated protein expressed in migrating and differentiating neurons

Recently, we and others reported that the doublecortin gene is responsible for X-linked lissencephaly and subcortical laminar heterotopia. Here, we show that Doublecortin is expressed in the brain throughout the period of corticogenesis in migrating and differentiating neurons. Immunohistochemical studies show its localization in the soma and leading processes of tangentially migrating neurons, and a strong axonal labeling is observed in differentiating neurons. In cultured neurons, Doublecortin expression is highest in the distal parts of developing processes. We demonstrate by sedimentation and microscopy studies that Doublecortin is associated with microtubules (MTs) and postulate that it is a novel MAP. Our data suggest that the cortical dysgeneses associated with the loss of Doublecortin function might result from abnormal cytoskeletal dynamics in neuronal cell development.

The DNA sequence of human chromosome 21

Chromosome 21 is the smallest human autosome. An extra copy of chromosome 21 causes Down syndrome, the most frequent genetic cause of significant mental retardation, which affects up to 1 in 700 live births. Several anonymous loci for monogenic disorders and predispositions for common complex disorders have also been mapped to this chromosome, and loss of heterozygosity has been observed in regions associated with solid tumours. Here we report the sequence and gene catalogue of the long arm of chromosome 21. We have sequenced 33,546,361 base pairs (bp) of DNA with very high accuracy, the largest contig being 25,491,867 bp. Only three small clone gaps and seven sequencing gaps remain, comprising about 100 kilobases. Thus, we achieved 99.7% coverage of 21q. We also sequenced 281,116 bp from the short arm. The structural features identified include duplications that are probably involved in chromosomal abnormalities and repeat structures in the telomeric and pericentromeric regions. Analysis of the chromosome revealed 127 known genes, 98 predicted genes and 59 pseudogenes.

Analysis of the tandem repeat locus D4Z4 associated with facioscapulohumeral muscular dystrophy

The sequence of the tandem repeat sequence (D4Z4) associated with facioscapulohumeral muscular dystrophy (FSHD) has been determined: each copy of the 3.3 kb repeat contains two homeoboxes and two previously described repetitive sequences, LSau and a GC-rich low copy repeat designated hhspm3. By Southern blotting, FISH and isolation of cDNA and genomic clones we show that there are repeat sequences similar to D4Z4 at other locations in the human genome. Southern blot analysis of primate genomic DNA indicates that the copy number of D4Z4-like repeats has increased markedly within the last 25 million years. Two cDNA clones were isolated and found to contain stop codons and frameshifts within the homeodomains. An STS was produced to the cDNAs and analysis of a somatic cell hybrid panel suggests they map to chromosome 14. No cDNA clones mapping to the chromosome 4q35 D4Z4 repeats have been identified, although the possibility that they encode a protein cannot be ruled out. Although D4Z4 may not encode a protein, there is an association between deletions within this locus and FSHD. The D4Z4 repeats contain LSau repeats and are adjacent to 68 bp Sau3A repeats. Both of these sequences are associated with heterochromatic regions of DNA, regions known to be involved in the phenomenon of position effect variegation. We postulate that deletion of D4Z4 sequences could produce a position effect.

Doublecortin, a stabilizer of microtubules

X-linked lissencephaly is a severe brain malformation affecting males. Recently it has been demonstrated that the doublecortin gene is implicated in this disorder. In order to study the function of Doublecortin, we analyzed the protein upon transfection of COS cells. Doublecortin was found to bind to the microtubule cytoskeleton. In vitro assays (using biochemical methods, DIC microscopy and electron microscopy) demonstrate that Doublecortin binds microtubules directly, stabilizes them and causes bundling. In vivo assays also show that Doublecortin stabilizes microtubules and causes bundling. Doublecortin is a basic protein with an iso-electric point of 10, typical of microtubule-binding proteins. However, its sequence contains no known microtubule-binding domain(s). The results obtained in this study with Doublecortin and our previous work on another lissencephaly gene ( LIS1 ) emphasize the central role of regulation of microtubule dynamics and stability during neuronal morphogenesis.

High resolution cosmid and P1 maps spanning the 14 Mb genome of the fission yeast S. pombe

Gridded on high density filters, a P1 genomic library of 17-fold coverage and a cosmid library of 8 genome equivalents, both made from S. pombe strain 972h-, were ordered by hybridizing genetic markers and individual clones from the two libraries. Yeast artificial chromosome (YAC) clones covering the entire genome were used to subdivide the libraries, and hybridization of short oligonucleotides and DNA pools made from randomly selected cosmids provided further mapping information. Restriction digests were generated as an independent confirmation of the clone order. The high resolution clone map was aligned to the genetic map and the physical Notl and YAC maps. The usefulness of the various mapping techniques and cloning procedures could be assessed upon the different data sets.

doublecortin is the major gene causing X-linked subcortical laminar heterotopia (SCLH)

Subcortical laminar heterotopia (SCLH), or 'double cortex', is a cortical dysgenesis disorder associated with a defect in neuronal migration. Clinical manifestations are epilepsy and mental retardation. This disorder, which mainly affects females, can be inherited in a single pedigree with lissencephaly, a more severe disease which affects the male individuals. This clinical entity has been described as X-SCLH/LIS syndrome. Recently we have demonstrated that the doublecortin gene, which is localized on the X chromosome, is implicated in this disorder. We have now performed a systematic mutation analysis of doublecortin in 11 unrelated females with SCLH (one familial and 10 sporadic cases) and have identified mutations in 10/11 cases. The sequence differences include nonsense, splice site and missense mutations and these were found throughout the gene. These results provide strong evidence that loss of function of doublecortin is the major cause of SCLH. The absence of phenotype-genotype correlations suggests that X-inactivation patterns of neuronal precursor cells are likely to contribute to the variable clinical severity of this disorder in females.

A new gene involved in X-linked mental retardation identified by analysis of an X;2 balanced translocation

X-linked forms of mental retardation (MR) affect approximately 1 in 600 males and are likely to be highly heterogeneous. They can be categorized into syndromic (MRXS) and nonspecific (MRX) forms. In MRX forms, affected patients have no distinctive clinical or biochemical features. At least five MRX genes have been identified by positional cloning, but each accounts for only 0.5%-1.0% of MRX cases. Here we show that the gene TM4SF2 at Xp11.4 is inactivated by the X breakpoint of an X;2 balanced translocation in a patient with MR. Further investigation led to identification of TM4SF2 mutations in 2 of 33 other MRX families. RNA in situ hybridization showed that TM4SF2 is highly expressed in the central nervous system, including the cerebral cortex and hippocampus. TM4SF2 encodes a member of the tetraspanin family of proteins, which are known to contribute in molecular complexes including beta-1 integrins. We speculate that through this interaction, TM4SF2 might have a role in the control of neurite outgrowth.

Identification of aphid salivary proteins: a proteomic investigation of Myzus persicae

The role of insect saliva in the first contact between an insect and a plant is crucial during feeding. Some elicitors, particularly in insect regurgitants, have been identified as inducing plant defence reactions. Here, we focused on the salivary proteome of the green peach aphid, Myzus persicae. Proteins were either directly in-solution digested or were separated by 2D SDS-PAGE before trypsin digestion. Resulting peptides were then identified by mass spectrometry coupled with database investigations. A homemade database was constituted of expressed sequence tags from the pea aphid Acyrtosiphon pisum and M. persicae. The databases were used to identify proteins related to M. persicae with a nonsequenced genome. This procedure enabled us to discover glucose oxidase, glucose dehydrogenase, NADH dehydrogenase, alpha-glucosidase and alpha-amylase in M. persicae saliva. The presence of these enzymes is discussed in terms of plant-aphid interactions.

Distribution of mutations in the PEX gene in families with X-linked hypophosphataemic rickets (HYP)

Mutations in the PEX gene at Xp22.1 (phosphate-regulating gene with homologies to endopeptidases, on the X-chromosome), are responsible for X-linked hypophosphataemic rickets (HYP). Homology of PEX to the M13 family of Zn2+ metallopeptidases which include neprilysin (NEP) as prototype, has raised important questions regarding PEX function at the molecular level. The aim of this study was to analyse 99 HYP families for PEX gene mutations, and to correlate predicted changes in the protein structure with Zn2+ metallopeptidase gene function. Primers flanking 22 characterised exons were used to amplify DNA by PCR, and SSCP was then used to screen for mutations. Deletions, insertions, nonsense mutations, stop codons and splice mutations occurred in 83% of families screened for in all 22 exons, and 51% of a separate set of families screened in 17 PEX gene exons. Missense mutations in four regions of the gene were informative regarding function, with one mutation in the Zn2+-binding site predicted to alter substrate enzyme interaction and catalysis. Computer analysis of the remaining mutations predicted changes in secondary structure, N-glycosylation, protein phosphorylation and catalytic site molecular structure. The wide range of mutations that align with regions required for protease activity in NEP suggests that PEX also functions as a protease, and may act by processing factor(s) involved in bone mineral metabolism.

An overview of odorant-binding protein functions in insect peripheral olfactory reception

Insect olfactory perception involves many aspects of insect life, and can directly or indirectly evoke either individual or group behaviors. Insect olfactory receptors and odorant-binding proteins (OBPs) are considered to be crucial to insect-specific and -sensitive olfaction. Although the mechanisms of interaction between OBPs or OBP/ligand complex with olfactory receptors are still not well understood, it has been shown that many OBPs contribute to insect olfactory perception at various levels. Some of these are numerous and divergent members in OBP family; expression in the olfactory organ at high concentration; a variety of combinational patterns between different OBPs and ligands, but exclusive affinity for one OBP to specific binding ligands; complicated interactions between OBP/ligand complex and transmembrane proteins (olfactory receptors or sensory neuron membrane proteins). First, we review OBPs' ligand-binding property based on OBP structural research and ligand-binding test; then, we review current progress around the points cited above to show the role of such proteins in insect olfactory signal transmission; finally, we discuss applications based on insect OBP research.

Pex gene deletions in Gy and Hyp mice provide mouse models for X-linked hypophosphatemia

X-linked hypophosphatemic rickets in humans is caused by mutations in the PEX gene which codes for a protein homologous to neutral endopeptidases. Hyp and Gy mice both have X-linked hypophosphatemic rickets, although genetic data and the different phenotypic spectra observed have previously suggested that two different genes are mutated. In addition to the metabolic disorder observed in Hyp mice, male Gy mice are sterile and show circling behavior and reduced viability. We now report the cloning of the mouse homolog of PEX which is highly conserved between man and mouse. The 3' end of this gene is deleted in Hyp mice. In Gy mice, the first three exons and the promotor region are deleted. Thus, Hyp and Gy are allelic mutations and both provide mouse models for X-linked hypophosphatemia.

Genomic organization of the human PEX gene mutated in X-linked dominant hypophosphatemic rickets

X-linked dominant hypophosphatemic rickets (HYP) is the most common form of hereditary rickets. Recently we have cloned thePEX gene and shown it to be mutated and deleted in HYP individuals. We have now completely sequenced a 243-kb genomic region containing PEX and have identified all intron–exon boundary sequences. We show that PEX, homologous to members of a neutral endopeptidase family, has an exon organization that is very similar to neprilysin. We have performed an extensive mutation analysis examining all 22 PEX coding exons in 29 familial and 14 sporadic cases of hypophosphatemia. Sequence changes include missense, frameshift, nonsense, and splice site mutations and intragenic deletions. A mutation was found in 25 (86%) of the 29 familial cases and 8 (57%) of the 14 sporadic cases. Our data provide the first evidence that most of the familial and also a large number of the sporadic cases of hypophosphatemia are caused by loss-of-function mutations in PEX.

[The sequence data described in this paper have been submitted to GenBank under accession nos.Y08111–Y08132 and Y10196.]

Effects of allelochemicals from first (brassicaceae) and second (Myzus persicae and Brevicoryne brassicae) trophic levels on Adalia bipunctata

Three Brassicaceae species, Brassica napus (low glucosinolate content), Brassica nigra (including sinigrin), and Sinapis alba (including sinalbin) were used as host plants for two aphid species: the generalist Myzus persicae and the specialist Brevicoryne brassicae. Each combination of aphid species and prey host plant was used to feed the polyphagous ladybird beetle, Adalia bipunctata. Experiments with Brassicaceae species including different amounts and kinds of glucosinolates (GLS) showed increased ladybird larval mortality at higher GLS concentrations. When reared on plants with higher GLS concentrations, the specialist aphid, B. brassicae, was found to be more toxic than M. persicae. Identification of GLS and related degradation products, mainly isothiocyanates (ITC), was investigated in the first two trophic levels, plant and aphid species, by high-performance liquid chromatography and gas chromatography-mass spectrometry, respectively. While only GLS were detected in M. persicae on each Brassicaceae species, high amounts of ITC were identified in B. brassicae samples (allyl-ITC and benzyl-ITC from B. nigra and S. alba, respectively) from all host plants. Biological effects of allelochemicals from plants on predators through aphid prey are discussed in relation to aphid species to emphasize the role of the crop plant in integrated pest management in terms of biological control efficacy.

Doublecortin mutations cluster in evolutionarily conserved functional domains

Mutations in the X-linked gene doublecortin ( DCX ) result in lissencephaly in males or subcortical laminar heterotopia ('double cortex') in females. Various types of mutation were identified and the sequence differences included nonsense, splice site and missense mutations throughout the gene. Recently, we and others have demonstrated that DCX interacts and stabilizes microtubules. Here, we performed a detailed sequence analysis of DCX and DCX-like proteins from various organisms and defined an evolutionarily conserved Doublecortin (DC) domain. The domain typically appears in the N-terminus of proteins and consists of two tandemly repeated 80 amino acid regions. In the large majority of patients, missense mutations in DCX fall within the conserved regions. We hypothesized that these repeats may be important for microtubule binding. We expressed DCX or DCLK (KIAA0369) repeats in vitro and in vivo. Our results suggest that the first repeat binds tubulin but not microtubules and enhances microtubule polymerization. To study the functional consequences of DCX mutations, we overexpressed seven of the reported mutations in COS7 cells and examined their effect on the microtubule cytoskeleton. The results demonstrate that some of the mutations disrupt microtubules. The most severe effect was observed with a tyrosine to histidine mutation at amino acid 125 (Y125H). Produced as a recombinant protein, this mutation disrupts microtubules in vitro at high molar concentration. The positions of the different mutations are discussed according to the evolutionarily defined DC-repeat motif. The results from this study emphasize the importance of DCX-microtubule interaction during normal and abnormal brain development.

Autism and multiple exostoses associated with an X;8 translocation occurring within the GRPR gene and 3' to the SDC2 gene

An X;8 translocation was identified in a 27-year-old female patient manifesting multiple exostoses and autism accompanied by mental retardation and epilepsy. Through molecular analysis using yeast artificial chromosomes (YACs) and cosmid clones, the translocation breakpoint was isolated and confirmed to be reciprocal within a 5'-GGCA-3' sequence found on both X and 8 chromosomes without gain or loss of a single nucleotide. The translocation breakpoint on the X chromosome occurred in the first intron of the gastrin-releasing peptide receptor (GRPR) gene and that on chromosome 8 occurred approximately 30 kb distal to the 3' end of the Syndecan-2 gene (SDC2), also known as human heparan sulfate proteoglycan or fibroglycan. The GRPR gene was shown to escape X-inactivation. A dosage effect of the GRPR and a position effect of the SDC2 gene may, however, contribute the phenotype observed in this patient since the orientation of these genes with respect to the translocation was incompatible with the formation of a fusion gene. Investigation of mutations in these two genes in unrelated patients with either autism or multiple exostoses as well as linkage and association studies is needed to validate them as candidate genes.

Comparative analyses of salivary proteins from three aphid species

Saliva is a critical biochemical interface between aphids and their host plants; however, the biochemical nature and physiological functions of aphid saliva proteins are not fully elucidated. In this study we used a multidisciplinary proteomics approach combining liquid chromatography-electrospray ionization tandem mass spectrometry and two-dimensional differential in-gel electrophoresis/matrix-assisted laser desorption/ionization time-of-flight/mass spectrometry to compare the salivary proteins from three aphid species including Acyrthosiphon pisum, Megoura viciae and Myzus persicae. Comparative analyses revealed variability among aphid salivary proteomes. Among the proteins that varied, 22% were related to DNA-binding, 19% were related to GTP-binding, and 19% had oxidoreductase activity. In addition, we identified a peroxiredoxin enzyme and an ATP-binding protein that may be involved in the modulation of plant defences. Knowledge of salivary components and how they vary among aphid species may reveal how aphids target plant processes and how the aphid and host plant interact.

The genomic organization of NKG2C, E, F, and D receptor genes in the human natural killer gene complex

Interactions of natural killer cell receptors with their cognate ligands play a major role in regulating NK cell function. The NKG2 gene family encodes several highly similar proteins, which are known to form heterodimers with the CD94 receptor. These dimers play a role in the inhibition as well as the activation of NK cells. We have analyzed the gene structures of the NKG2C, D, E, and F genes, and determined their genomic organization. Restriction mapping and sequencing revealed the four genes to be closely linked to one another, and of the same transcriptional orientation. An exon duplication within the NKG2C and E genes was identified, although the duplicated version of this exon has not yet been found in mRNA sequences. The NKG2C, E, and F genes, despite being highly similar, are variable at their 3' ends. We show that NKG2C consists of six exons, whereas NKG2E has seven, and the splice acceptor site for the seventh exon occurs in an Alu repeat. NKG2F consists of only four exons and part of exon IV is in some cases spliced to the 5' end of the NKG2D transcript. NKG2D has only a low similarity to the other NKG2 genes.

Hippocampal development - old and new findings

The hippocampus, derived from medial regions of the telencephalon, constitutes a remarkable brain structure. It is part of the limbic system, and it plays important roles in information encoding, related to short-term and long-term memory, and spatial navigation. It has also attracted the attention of many clinicians and neuroscientists for its involvement in a wide spectrum of pathological conditions, including epilepsy, intellectual disability, Alzheimer disease and others. Here we address the topic of hippocampal development. As well as original landmark findings, modern techniques such as large-scale in situ hybridizations, in utero electroporation and the study of mouse mutants with hippocampal phenotypes, add further detail to our knowledge of the finely regulated processes which form this intricate structure. Molecular signatures are being revealed related to field, intra-field and laminar cell identity, as well as, cell compartments expressing surface proteins instrumental for connectivity. We summarize here old and new findings, and highlight elegant tools used to fine-study hippocampal development.

A cosmid contig and high resolution restriction map of the 2 megabase region containing the Huntington's disease gene

The quest for the mutation responsible for Huntington's disease (HD) has required an exceptionally detailed analysis of a large part of 4p16.3 by molecular genetic techniques, making this stretch of 2.2 megabases one of the best characterized regions of the human genome. Here we describe the construction of a cosmid and P1 clone contig spanning the region containing the HD gene, and the establishment of a detailed, high resolution restriction map. This ordered clone library has allowed the identification of several genes from the region, and has played a vital role in the recent identification of the Huntington's disease gene. The restriction map provides the framework for the detailed analysis of a region extremely rich in coding sequences. This study also exemplifies many of the strategies to be used in the analysis of larger regions of the human genome.

Sinonasal undifferentiated carcinoma: a 10-year experience

PURPOSE

Sinonasal undifferentiated carcinoma (SNUC) is a rare and aggressive malignancy of the paranasal sinuses and nasal cavity. Of the few reported series, most indicate a dismal prognosis. In this report, the clinical presentation, histopathologic criteria used for diagnosis, mode of treatment, and outcome are evaluated in seven patients with SNUC.

MATERIALS AND METHODS

Seven patients with SNUC treated at the University of Cincinnati between 1983 and 1993 were analyzed retrospectively.

RESULTS

Most of the patients presented with extensive local disease, and two patients also had cervical metastases. All except one were treated using a multimodality approach. Four of the seven patients died of disease (DOD), with a mean survival of only 11.5 months following treatment. Inability to eradicate local disease was responsible for treatment failure in all cases. Three patients have achieved short-term control of disease following combined therapy, but one is at high risk for recurrence.

CONCLUSION

SNUC was associated with an overall poor prognosis in our series despite aggressive treatment. Control of local disease was the central therapeutic consideration. Intensive multimodality therapy is recommended for all patients with SNUC.

Doublecortin interacts with mu subunits of clathrin adaptor complexes in the developing nervous system

Doublecortin is a microtubule-associated protein required for normal corticogenesis in the developing brain. We carried out a yeast two-hybrid screen to identify interacting proteins. One of the isolated clones encodes the mu1 subunit of the adaptor complex AP-1 involved in clathrin-dependent protein sorting. We found that Doublecortin also interacts in yeast with mu2 from the AP-2 complex. Mutagenesis and pull-down experiments showed that these interactions were mediated through a tyrosine-based sorting signal (YLPL) in the C-terminal part of Doublecortin. The functional relevance of these interactions was suggested by the coimmunoprecipitation of Doublecortin with AP-1 and AP-2 from mouse brain extracts. This interaction was further supported by RNA in situ hybridization and immunofluorescence studies. Taken together these data indicate that a certain proportion of Doublecortin interacts with AP-1 and/or AP-2 in vivo and are consistent with a potential involvement of Doublecortin in protein sorting or vesicular trafficking.

Non-random distribution of mutations in the PHEX gene, and under-detected missense mutations at non-conserved residues

Thirty newly detected mutations in the PHEX gene are reported, and pooled with all the previously published mutations. The spectrum of mutations displayed 16% deletions, 8% insertions, 34% missense, 27% nonsense, and 15% splice site mutations, with two peaks in exon 15, and 17. Since 32.8% of PHEX amino acids were conserved in the endopeptidases family, the number of missense mutations detected at non-conserved residues was smaller than expected, whereas the number of nonsense mutations observed at non-conserved residues was very close to the expected number. Compared with conserved amino acids, the changes in non-conserved amino acids may result in benign polymorphisms or possibly mild disease that may go undiagnosed.

The gene for X-linked hypophosphataemic rickets maps to a 200-300kb region in Xp22.1, and is located on a single YAC containing a putative vitamin D response element (VDRE)

The location of the HYP gene, which determines X-linked hypophosphataemic rickets, has been refined considerably by linkage analysis, and three new microsatellite primers isolated, Cap32 (DXS7473), Cap29 (DXS7474) and 7v2 (DXS7475). The locations of four other markers have also been determined (DXS1226, AFMa176zb1, AFMa152wc5, and AFM346azc1). Markers Cap29 and Cap32 are the closest distal markers to the gene with zetamax=11.93, thetamax= 0.018 and zetamax=12.03, thetamax = 0.015 respectively. Both Cap29 and Cap32 are proximal to DXS365 and AFMa176zb1, as deduced by screening non-chimaeric yeast artificial chromosomes (YACs) from a contig spanning the HYP gene. A single crossover places AFMa176zbl distal to the disease gene. There are no recombinations between 7v2 and HYP (zetamax=12.9, thetamax=0.0), or between 7v2 and adjacent markers Cap32, Cap29, AFMa176zb1, DXS1683 and DXS365. However screening of YAC clones encompassing the HYP gene and also P1 clones localises 7v2 distal to Cap29 and Cap32, and proximal to DXS443. Marker DXS1226 is placed outside the region containing the gene, and is located proximal to DXS274 as confirmed by a crossover for this marker and DXS41 against HYP and its presence on YAC 83B05. Genetic mapping of CEPH pedigrees, and screening of YACs places AFMa152wc5 and AFMa346zcl between DXS1683 and DXS1052. The following gene marker map presents the best order for the HYP region: Xptel-DXS43-DXS999-DXS443-(DXS365/DXS74 75/AFMa176zb1)-(DXS7474/DXS7473)-HYP- DXS1683-(AFMa152wc5/AFMa346zc1)-DXS1052-DXS 274 -(DXS41/DXS1226)-Xcen. The distance between the cluster of distal flanking markers Cap29 (DXS7474), Cap32 (DXS7473), and DXS1683 is approximately 300 kb, as deduced from physical map data from a YAC contig spanning the gene. Thus the gene for HYP is contained within a single YAC (900AO472). Of further interest, is the location of a putative vitamin D response element (VDRE) on this YAC.

Spermine deficiency in Gy mice caused by deletion of the spermine synthase gene

Two mouse mutations gyro (Gy) and hypophosphatemia (Hyp) are mouse models for X-linked hypophosphatemic rickets and have been shown to be deleted for the 5' and 3' end of the mouse homolog of PHEX (phosphate regulating gene with homologies to endopeptidases on the X chromosome; formerly called PEX), respectively. In addition to the metabolic disorder observed in Hyp mice, male Gy mice are sterile and show circling behavior and reduced viability. The human SMS (spermine synthase) gene maps approximately 39 kb upstream of PHEX and is transcribed in the same direction. To elucidate the complex phenotype of Gy mice, we characterized the genomic region upstream of Phex. By establishing the genomic structure of mouse Sms, a 160-190 kb deletion was shown in Gy mice, which includes both Phex and Sms. There are several pseudogenes of SMS / Sms in man and mouse. Northern analysis revealed three different Sms transcripts which are absent in Gy mice. Measurement of polyamine levels revealed a marked decrease in spermine in liver and pancreas of affected male Gy mice. Analysis of brain tissue revealed no gross or histological abnormalities. Gy provides a mouse model for a defect in the polyamine pathway, which is known to play a key role in cell proliferation.