Cancer spectrum and frequency among children with Noonan, Costello, and cardio-facio-cutaneous syndromes

Background:

Somatic mutations affecting components of the Ras-MAPK pathway are a common feature of cancer, whereas germline Ras pathway mutations cause developmental disorders including Noonan, Costello, and cardio-facio-cutaneous syndromes. These ‘RASopathies' also represent cancer-prone syndromes, but the quantitative cancer risks remain unknown.

Methods:

We investigated the occurrence of childhood cancer including benign and malignant tumours of the central nervous system in a group of 735 individuals with germline mutations in Ras signalling pathway genes by matching their information with the German Childhood Cancer Registry.

Results:

We observed 12 cases of cancer in the entire RASopathy cohort vs 1.12 expected (based on German population-based incidence rates). This corresponds to a 10.5-fold increased risk of all childhood cancers combined (standardised incidence ratio (SIR)=10.5, 95% confidence interval=5.4–18.3). The specific cancers included juvenile myelomonocytic leukaemia=4; brain tumour=3; acute lymphoblastic leukaemia=2; rhabdomyosarcoma=2; and neuroblastoma=1. The childhood cancer SIR in Noonan syndrome patients was 8.1, whereas that for Costello syndrome patients was 42.4.

Conclusions:

These data comprise the first quantitative evidence documenting that the germline mutations in Ras signalling pathway genes are associated with increased risks of both childhood leukaemia and solid tumours.

Phenotypic spectrum of epidermolysis bullosa associated with α6β4 integrin mutations

BACKGROUND

Integrin α6β4 is a transmembrane receptor and a key component of the hemidesmosome anchoring complex. It is involved in cell-matrix adhesion and signalling in various tissues. Mutations in the ITGA6 and ITGB4 genes coding for α6β4 integrin compromise dermal-epidermal adhesion and are associated with skin blistering and pyloric atresia (PA), a disorder known as epidermolysis bullosa with PA (EB-PA).

OBJECTIVES

To elucidate the molecular pathology of skin fragility in eight cases, disclose the underlying ITGA6 and ITGB4 mutations and study genotype-phenotype correlations.

METHODS

DNA was isolated from ethylenediaminetetraacetic acid-blood samples, and the coding exons and exon-intron boundaries of ITGA6 and ITGB4 were amplified by polymerase chain reaction (PCR), and directly sequenced. Skin samples were submitted to immunofluorescence mapping with antibodies to adhesion proteins of the dermal-epidermal junction. Primary keratinocytes were isolated, and used for RNA and protein extraction, reverse transcription PCR and immunoblotting. Ultrastructural analysis of the skin was performed in one patient.

RESULTS

We disclose 10 novel mutations, one in ITGA6 and nine in ITGB4. Skin cleavage was either intraepidermal or junctional. Lethal outcome and PA correlated with loss-of-function mutations in two cases. Solely mild skin involvement was associated with deletion of the C-terminus of β4 integrin. Combinations of missense, nonsense or frameshift mutations caused severe urinary tract involvement in addition to skin fragility in five cases.

CONCLUSIONS

The present study reveals novel ITGA6 and ITGB4 gene mutations and supports previous reports showing that the phenotype may lack PA and be limited to skin and nail involvement. In four out of six cases of EB-PA, life expectancy was not impaired. A high frequency of urinary tract involvement was found in this study, and represented the main cause of morbidity. Low levels of β4 integrin expression were compatible with hemidesmosomal integrity and a mild skin phenotype.

Late-onset inversa recessive dystrophic epidermolysis bullosa caused by glycine substitutions in collagen type VII

Dystrophic epidermolysis bullosa (DEB) is a rare hereditary skin disorder caused by mutations in COL7A1, encoding collagen type VII.1 Clinical manifestations of COL7A1 mutations range from generalized skin blistering to mild localized blistering or nail dystrophy.2 The investigation of the molecular basis of DEB has revealed more than 540 different mutations that cannot entirely explain phenotypic variations (HGMD Professional 2010.3, https://portal.biobase-international. com/hgmd/). Inversa recessive DEB (RDEB-I) is a subtype characterized by generalized blistering in the neonatal period. The condition improves with age, and in adults blistering is restricted to intertriginous areas, and severe lesions of the oral and genital mucosa and nail changes occur in the majority of described patients.2 Recent data suggested that amino-acid substitutions affecting arginines or glycines at borders of collagenic subdomains might cause this phenotype.3 We report a German patient with an unusually mild RDEB-I harbouring compound heterozygous mutations in COL7A1.

Poikiloderma with neutropenia: a novel C16orf57 mutation and clinical diagnostic criteria

A new syndrome with poikiloderma was described by Clericuzio et al. in 1991.(1) They reported 14 Navajo native Americans, including eight siblings, developing in the first year of life an erythematous rash, which started on the limbs and spread over the trunk and the face. This rash evolved into poikiloderma. All patients had recurrent bacterial infections. First published as Navajo poikiloderma this syndrome is now known as poikiloderma with neutropenia (PN, OMIM 604173). The inheritance is autosomal recessive, and mutations in a new gene, C16orf57, were recently described in two kindreds.(2) Because of the phenotypic overlap between Rothmund-Thomson syndrome (RTS) and PN, a few patients have been reclassified as mutations in the RECQL4 gene for RTS were absent.(2-5) Until now 27 patients have been described with clinical PN.(1-3,5-8) Here, we report the sixth family with PN outside the Navajo population. We found the previously unreported mutation c.243G>A, p.W81X in the C16orf57 gene, thus confirming the relation of this gene to the disease.(2,6) Because the molecular genetic diagnosis is not always available, we propose clinical and laboratory diagnostic criteria for PN.

Multiple malignant diseases in a patient with Rothmund-Thomson syndrome with RECQL4 mutations: Case report and literature review

RECQL4 mutations cause genetic instability and increase the risk of malignant disease. We report on a patient with compound heterozygosity for two novel RECQL4 mutations: mutation c.1919_1924delTCACAG, p.L640_A642delinsP in exon 12 of the RECQL4 gene and mutation c.1704+1G>A in intron 10 of the RECQL4 gene. He subsequently developed large cell anaplastic T cell lymphoma at the age of 9 years, diffuse large cell B lymphoma and osteosarcoma when he was 14 years old, and finally acute lymphatic leukemia when he was 21 years old. The most remarkable clinical features are young age, spontaneous remission of diffuse large cell lymphoma, and severe CNS and skin toxicity of cytotoxic treatment.

[Glycogenosis type IV (Andersen disease). Clinical data, pathology, and genetics in a fatal perinatal case]

Here we report the case of a newborn with glycogenosis type IV (Andersen disease), who died shortly after birth. The diagnosis was established in the first instance by light microscopy and histochemistry, and subsequently ultrastructurally. DNA could be extracted from a fibroblast cell culture by sequencing the causative GBE1 gene (glycogen branching enzyme 1). Two compound heterozygous mutations in the gene were identified. The differential diagnosis should include Lafora disease as well as polyglucosan body disease. Since there is no effective therapy for glycogenosis type IV to date, prenatal diagnosis is mandatory.

Severe phenotype in a girl with partial tetrasomy 7, karyotype 46,XX,trp(7)(q35q36)

On prenatal ultrasonography, polyhydramnion, internal hydrocephalus, hypoplasia of the corpus callosum, and dysmorphic features were detected in a fetus of a 22-year-old mother. Subsequent karyotyping of amniocytes revealed supernumerary material in distal 7q. The baby was delivered after 38+4 weeks of gestation, and postnatal array CGH analysis showed a triplication of 7q35-->q36, resulting in partial tetrasomy. The triplication was not distinguishable from a duplication by conventional and molecular cytogenetic methods, but was clearly identified by array CGH analysis. The phenotype was rather severe with limited cardiac contractility and subsequent respiratory problems, as well as progressive neurologic deterioration and several dysmorphic features. Triplications in general are rare, and this case is the first report of a microscopically visible triplication in 7q. Duplication patients of the same chromosomal segment also showed a severe phenotype, however, in our opinion there are no common features suggesting a clinically recognizable distal 7q duplication/triplication syndrome.

Forty-two novel COL7A1 mutations and the role of a frequent single nucleotide polymorphism in the MMP1 promoter in modulation of disease severity in a large European dystrophic epidermolysis bullosa cohort

BACKGROUND

Dystrophic epidermolysis bullosa (DEB) is a severe genetic skin blistering disorder caused by mutations in the gene COL7A1, encoding collagen VII. Recently, the MMP1 promoter single nucleotide polymorphism (SNP) rs1799750, designated as 1G 2G, was shown to be involved in modulation of disease severity in patients with recessive DEB (RDEB), and was proposed as a genetic modifier.

OBJECTIVES

To identify the molecular basis of DEB in 103 individuals and to replicate the results of the MMP1 promoter SNP analysis in an independent patient group, as verification is necessary in such a rare and heterogeneous disorder.

METHODS

To determine the molecular basis of the disease, we performed COL7A1 mutation screening, reverse transcription-polymerase chain reaction (PCR) and real-time quantitative PCR. The status of the MMP1 SNP was analysed by PCR and restriction enzyme digestion and verified by sequencing.

RESULTS

We disclosed 42 novel COL7A1 mutations, including the first large genomic deletion of 4 kb affecting only the COL7A1 gene, and three apparently silent mutations affecting splicing. Even though the frequency of the high-risk allele was increased in patients with RDEB, no statistically significant correlation between disease severity and genotype could be made. Also, no correlation was observed with development of squamous cell carcinoma, a severe complication of DEB.

CONCLUSIONS

Taken together, the results suggest that the MMP1 SNP is not the sole disease modifier in different forms of DEB, and other genetic and environmental factors contribute to the clinical phenotype.

[Hereditary Alzheimer's disease with amyloid angiopathy caused by amyloid precursor protein locus]

We report a patient with early-onset autosomal dominant dementia. The CSF showed increased levels of tau protein and decreased amyloid beta (ratio 42:40) typical for Alzheimer's disease. Cerebral MRI revealed vascular lesions and white-matter changes around the posterior horns of the ventricles with only moderate atrophy of the brain. Susceptibility-weighted imaging detected multiple small hemorrhagic changes. Gene analysis revealed amyloid precursor protein (APP) locus duplication as the cause of hereditary Alzheimer's dementia. The co-occurrence of CSF changes typical for Alzheimer's disease and MRI findings of cerebral amyloid angiopathy is remarkable, as it is also described for APP locus duplication. In conjunction with a family history suggestive of hereditary dementia, such a constellation should lead to enhanced gene analysis.

C-terminally truncated kindlin-1 leads to abnormal adhesion and migration of keratinocytes

BACKGROUND

The Kindler syndrome (KS) protein kindlin-1 is a member of a protein complex that links cortical actin to integrins on the surface of basal keratinocytes. Loss of kindlin-1 leads to abnormalities of cell adhesion and motility, and to skin blistering and progressive poikiloderma as clinical symptoms.

OBJECTIVES

Here we investigated a severely affected patient, disclosed the mutation that caused the disease and delineated its biological consequences.

METHODS

Mutation screening of the kindlin-1 gene, KIND1 (now called FERMT1), was performed with polymerase chain reaction (PCR) amplification of all exons and sequencing. Mutated kindlin-1 was characterized by reverse transcriptase (RT)-PCR and immunoblotting, and genotype-phenotype correlations were analysed using immunohistochemical staining of skin biopsies and keratinocytes from the patient's skin. Cell adhesion and motility were assessed with functional tests.

RESULTS

We disclosed a splice site mutation in the first position of intron 13 of the FERMT1 gene, which caused skipping of exon 13. The short transcript partially escaped nonsense-mediated mRNA decay and was translated into a truncated protein.

CONCLUSION

A C-terminally truncated kindlin-1 in keratinocytes could not function correctly even if it were expressed.

Location and type of mutation in the LIS1 gene do not predict phenotypic severity

BACKGROUND

Lissencephaly is a neuronal migration disorder leading to absent or reduced gyration and a broadened but poorly organized cortex. The most common form of lissencephaly is isolated, referred as classic or type 1 lissencephaly. Type 1 lissencephaly is mostly associated with a heterozygous deletion of the entire LIS1 gene, whereas intragenic heterozygous LIS1 mutations or hemizygous DCX mutations in males are less common.

METHODS

Eighteen unrelated patients with type 1 lissencephaly were clinically and genetically assessed. In addition, patients with subcortical band heterotopia (n = 1) or lissencephaly with cerebellar hypoplasia (n = 2) were included.

RESULTS

Fourteen new and seven previously described LIS1 mutations were identified. We observed nine truncating mutations (nonsense, n = 2; frameshift, n = 7), six splice site mutations, five missense mutations, and one in-frame deletion. Somatic mosaicism was assumed in three patients with partial subcortical band heterotopia in the occipital-parietal lobes or mild pachygyria. We report three mutations in exon 11, including a frameshift which extends the LIS1 protein, leading to type 1 lissencephaly and illustrating the functional importance of the WD domains at the C terminus. Furthermore, we present two patients with novel LIS1 mutations in exon 10 associated with lissencephaly with cerebellar hypoplasia type a.

CONCLUSION

In contrast to previous reports, our data suggest that neither type nor position of intragenic mutations in the LIS1 gene allows an unambiguous prediction of the phenotypic severity. Furthermore, patients presenting with mild cerebral malformations such as subcortical band heterotopia or cerebellar hypoplasia should be considered for genetic analysis of the LIS1 gene.

Clinical and genetic features of families with frontotemporal dementia and parkinsonism linked to chromosome 17 with a P301S tau mutation

In 9 patients with frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) with a P301S tau mutation, the predominant phenotype was frontotemporal dementia in 3 and parkinsonism in 6. Comparison of the tau genotype/haplotype carrying the mutation and the initial clinical sign showed association between H1/H1 and parkinsonism and between H1/H2 and personality change. Thus, the tau haplotype carrying the mutation and the tau genotype may be related to the clinical phenotype throughout the disease course.

[Clinical and molecular genetic findings in isolated sporadic Duane syndrome]

BACKGROUND

Duane retraction syndrome (DURS) accounts for 1 - 4 % of all cases of strabismus. Approximately 90 % of the cases are sporadic with a preponderance for females and the left eye. Many associated ocular and systemic findings have been described. Recently, mutations of SALL4 have been found in patients with autosomal-dominantly inherited Okihiro syndrome (DURS associated with forearm malformations). The aim of this study was the clinical examination of patients with isolated sporadic DURS and the molecular genetic analysis of SALL4 in these patients.

SUBJECTS AND METHODS

Twenty-five patients with non-familial DURS (aged 1 - 75 years, 16 female, 9male) were examined clinically and were interviewed concerning associated pathologies. DNA was prepared from peripheral lymphocytes, and the complete coding region of SALL4 was sequenced.

RESULTS

In 18 patients DURS affected the left eye, in four the right eye, and was bilateral in three patients. One patient had fused vertebrae, one had a cone-rod-dystrophy. No hearing impairments or malformation of the upper limbs were observed. No mutation in the coding region of SALL4 could be detected.

DISCUSSION

Associated conditions in DURS patients most commonly involve the ear, the spinal column, the kidneys and the heart and the upper limbs. No mutations in SALL4 could be detected in patients with isolated sporadic DURS as opposed to findings in familial Okihiro syndrome. However, Okihiro syndrome shows marked intra- and interfamilial variability, suggesting that in rare cases of isolated DURS a causative SALL4 mutation may be found.

Cloning and expression analysis of SALL4, the murine homologue of the gene mutated in Okihiro syndrome

SALL4 is one out of four human homologues of the DROSOPHILA region-specific homeotic gene SPALT(SAL). Heterozygous mutations of SALL4 on chromosome 20q13.13--> q13.2 cause the autosomal dominant Okihiro syndrome which is characterized by radial limb defects, Duane anomaly and hearing loss. We have partially cloned the murine homologue of this gene, named SALL4, and completed the coding sequence by comparison to available EST and genomic sequences in the GenBank database. This comparison also revealed the chromosomal location of SALL4 on mouse chromosome 2H3 and suggested that a predicted testis expressed gene TEX20 at the very same locus is most likely not a gene on its own but part of the SALL4 3' UTR. We analyzed the expression of SALL4 during early embryogenesis by whole mount in situ hybridization and in the adult mouse by Northern blotting. In adult tissues, SALL4 expression is only found in testis and ovary. During embryonic development, SALL4 expression is widespread in early embryos and becomes gradually confined to the head region and the primitive streak. Prominent expression in the developing midbrain, branchial arches and the limbs suggests an important function of SALL4 during development of these structures as expected from the observation in Okihiro syndrome patients.

Mutations at the SALL4 locus on chromosome 20 result in a range of clinically overlapping phenotypes, including Okihiro syndrome, Holt-Oram syndrome, acro-renal-ocular syndrome, and patients previously reported to represent thalidomide embryopathy

We have recently shown that Okihiro syndrome results from mutation in the putative zinc finger transcription factor gene SALL4 on chromosome 20q13.13-13.2. There is considerable overlap of clinical features of Okihiro syndrome with other conditions, most notably Holt-Oram syndrome, a condition in part resulting from mutation of the TBX5 locus, as well as acro-renal-ocular syndrome. We analysed further families/patients with the clinical diagnosis of Holt-Oram syndrome and acro-renal-ocular syndrome for SALL4 mutations. We identified a novel SALL4 mutation in one family where the father was originally thought to have thalidomide embryopathy and had a daughter with a similar phenotype. We also found two novel mutations in two German families originally diagnosed as Holt-Oram syndrome and a further mutation in one out of two families carrying the diagnosis acro-renal-ocular syndrome. Our results show that some cases of "thalidomide embryopathy" might be the result of SALL4 mutations, resulting in an increased risk for similarly affected offspring. Furthermore we confirm the overlap of acro-renal-ocular syndrome with Okihiro syndrome at the molecular level and expand the phenotype of SALL4 mutations.

A novel family-specific translocation t(2;20)(p24.1;q13.1) associated with recurrent abortions: molecular characterization and segregation analysis in male meiosis

In the present study, we present a novel reciprocal translocation t(2;20)(p24.1;q13.1) and its segregation in a three generation family. The rate of miscarriages (50%) in pregnancies from male translocation carriers could be explained by unbalanced translocation-bearing spermatozoa found with a frequency of approximately 55% in the entire sperm population of a t(2;20)(p24.1;q13.1) carrier. These imbalanced spermatozoa mainly present as 2, der(20) and der(2), 20 missegregated (approximately 46%) while adjacent 2 and 3:1 segregation patterns account for approximately 5% and 4% of imbalances, respectively. While the translocation is associated clearly with an increased risk of early abortions (7/12) in both male and female carriers, no malformed livebirths were observed. Our results suggest complete embryonic lethality of imbalanced offspring. With respect to a high rate of segregation to 2, der(20) and to der(2), 20 imbalanced spermatozoa in male translocation carriers and with respect to known cases of partial trisomy 2p and 20q we consider that their corresponding monosomies result in fetal loss. This is the first study reporting multiple abortions associated with partial monosomy 20q13.1-->qter and 2pter-->p24.1 and the first report on the frequency of chromosomal imbalances in gametes of a male t(2;20)(p24.1;q13.1) heterozygote.

SALL1, the gene mutated in Townes-Brocks syndrome, encodes a transcriptional repressor which interacts with TRF1/PIN2 and localizes to pericentromeric heterochromatin

The Townes-Brocks syndrome (TBS) is an autosomal dominantly inherited malformation syndrome presenting as an association of imperforate anus, triphalangeal and supernumerary thumbs, malformed ears and sensorineural hearing loss. Mutations in SALL1, a gene mapping to 16q12.1, were identified as a cause for TBS. To elucidate how SALL1 mutations lead to TBS, we have performed a series of functional studies with the SALL1 protein. Using epifluorescence and confocal microscopy it could be shown that a GFP-SALL1 fusion protein localizes to chromocenters and smaller heterochromatin foci in transiently transfected NIH-3T3 cells. Chromocenters consist of clustered pericentromeric heterochromatin and contain telomere sequences. Indirect immunofluorescence revealed a partial colocalization of GFP-SALL1 with M31, the mouse homolog of the Drosophila heterochromatic protein HP1. It was further demonstrated that SALL1 acts as a strong transcriptional repressor in mammalian cells. Transcriptional repression could not be relieved by the addition of the histone deacetylase inhibitor Trichostatin-A. In a yeast two-hybrid screen we identified PIN2, an isoform of telomere-repeat-binding factor 1 (TRF1), as an interaction partner of SALL1, and showed that the N-terminus of SALL1 is not necessary for the interaction with PIN2/TRF1. The interaction was confirmed in vitro in a GST-pulldown assay. The association of the developmental regulator SALL1 with heterochromatin is striking and unexpected. Our results propose an involvement of SALL1 in the regulation of higher order chromatin structures and indicate that the protein might be a component of a distinct heterochromatin-dependent silencing process. We have also provided new evidence that there is a close functional link between the centromeric and telomeric heterochromatin domains not only in Drosophila and yeast, but also in mammalian cells.

Unique family with Townes-Brocks syndrome, SALL1 mutation, and cardiac defects

Townes-Brocks syndrome (TBS) is a condition with imperforate anus, hand anomalies, and ear malformations with sensorineural hearing loss. Many cases are sporadic. Within and between families, the phenotype displays striking variability. Recently, the disease-causing gene for TBS was identified as SALL1, a zinc finger transcription factor. Here, we report a three-generation family with seven affected individuals who have a novel SALL1 mutation. Unique cardiac anomalies seen in this family include lethal truncus arteriosus in one patient and a lethal complicated defect, including pulmonary valve atresia, in a second patient. These severe cardiac anomalies have not previously been reported in a familial case of TBS. This family and a review of the literature indicate that cardiac evaluation is warranted in all individuals with this disorder. In addition, hypoplastic thumbs were seen in two individuals in this family and should, therefore, be considered a true feature of TBS.

Unique family with Townes-Brocks syndrome, SALL1 mutation, and cardiac defects

Townes-Brocks syndrome (TBS) is a condition with imperforate anus, hand anomalies, and ear malformations with sensorineural hearing loss. Many cases are sporadic. Within and between families, the phenotype displays striking variability. Recently, the disease-causing gene for TBS was identified as SALL1, a zinc finger transcription factor. Here, we report a three-generation family with seven affected individuals who have a novel SALL1 mutation. Unique cardiac anomalies seen in this family include lethal truncus arteriosus in one patient and a lethal complicated defect, including pulmonary valve atresia, in a second patient. These severe cardiac anomalies have not previously been reported in a familial case of TBS. This family and a review of the literature indicate that cardiac evaluation is warranted in all individuals with this disorder. In addition, hypoplastic thumbs were seen in two individuals in this family and should, therefore, be considered a true feature of TBS.

Embryonic expression of the murine homologue of SALL1, the gene mutated in Townes--Brocks syndrome

SALL1 is one of three human homologues of the Drosophila region-specific homeotic gene spalt (sal). Mutations of SALL1 on chromosome 16q12.1 cause Townes--Brocks syndrome (TBS) which is characterized by defects in multiple organ systems including limbs, ears, kidneys and anus. Here, we have analyzed the expression of the mouse homologue of SALL1 (Sall1) during early embryogenesis. Sall1 expression is very prominent in the developing brain and the limbs. Other sites of expression include the meso- and metanephros, lens, olfactory bulbs, heart, primitive streak and the genital tubercle. Hence, Sall1 expression to a large degree reflects the structures affected in human TBS.

SALL1 mutations in Townes-Brocks syndrome and related disorders

Townes-Brocks syndrome (TBS) is a rare autosomal dominantly inherited malformation syndrome characterized by anal, renal, limb, and ear anomalies. TBS has been shown to result from mutations in SALL1, a human gene related to the developmental regulator sal of Drosophila melanogaster. The SALL1 gene product is a zinc finger protein thought to act as a transcription factor. It contains four highly conserved C2H2 double zinc finger domains which are evenly distributed. A single C2H2 motif is attached to the second domain, and at the amino terminus SALL1 contains a C2HC motif. Nineteen out of 20 SALL1 mutations known to date are located in exon 2, 5' of the third double zinc finger encoding region. These are nonsense mutations, short insertions, and short deletions, as well as one gross intraexonic deletion. One mutation within intron 2 creates an aberrant splice site. Most mutations lead to preterminal stop codons and are thought to cause the phenotype via haploinsufficiency. However, one short deletion results in a phenotype different from TBS which might be due to a dominant negative effect of a truncated SALL1 protein.

Molecular cloning, chromosomal localization, and expression of the murine SALL1 ortholog Sall1

SALL1 has been identified as one of now three human homologs of the region specific homeotic gene spalt (sal) of Drosophila, which encodes a zinc finger protein of characteristic structure. Mutations of SALL1 on chromosome 16q12.1 cause Townes-Brocks syndrome (TBS, OMIM no. 107480). In order to facilitate functional studies of this gene in a model organism, we searched for the murine homolog of SALL1. Here we report the genomic cloning, chromosome mapping, and partial expression analysis of the gene Sall1. Sequence comparison, Northern blot hybridization as well as the conserved chromosome location on the homologous mouse chromosome indicate that we have indeed isolated the murine homolog of SALL1.

Molecular cloning of a SALL1-related pseudogene and mapping to chromosome Xp11.2

SALL1 and SALL2 have been identified as two human homologs of the region-specific homeotic gene spalt (sal) of Drosophila, which encodes a zinc finger protein of characteristic structure. SALL1 has recently been found to be mutated in patients with Townes-Brocks syndrome (TBS, OMIM No. 107480). Here we report the isolation and mapping of another sal-like human gene, named SALL1P, on chromosome Xp11.2. This intronless gene closely resembles SALL1 but displays several mutations, suggesting that SALL1P represents a sal-related pseudogene. The high similarity of SALL1P to SALL1 is of considerable importance for mutation analysis of SALL1 in TBS.

First confirmed case with paternal uniparental disomy of chromosome 16

The existence of paternal uniparental disomy of chromosome 16 [upd(16)pat] has previously been suspected but has not been proven. We report prenatal detection and follow-up of isodisomic upd(16)pat in a child with minimal defects but otherwise normal development. Our results indicate that isodisomic upd(16)pat is associated with a normal outcome if no recessive mutation is reduced to homozygosity.

Genomic cloning, chromosomal mapping, and expression analysis of msal-2

Mutations of SALL1 related to spalt of Drosophila have been found to cause Townes-Brocks syndrome, suggesting a function of SALL1 for the development of anus, limbs, ears, and kidneys. No function is yet known for SALL2, another human spalt-like gene. The structure of SALL2 is different from SALL1 and all other vertebrate spalt-like genes described in mouse, Xenopus, and Medaka, suggesting that SALL2-like genes might also exist in other vertebrates. Consistent with this hypothesis, we isolated and characterized a SALL2 homologous mouse gene, Msal-2. In contrast to other vertebrate spalt-like genes both SALL2 and Msal-2 encode only three double zinc finger domains, the most carboxyterminal of which only distantly resembles spalt-like zinc fingers. The evolutionary conservation of SALL2/Msal-2 suggests that two lines of sal-like genes with presumably different functions arose from an early evolutionary duplication of a common ancestor gene. Msal-2 is expressed throughout embryonic development but also in adult tissues, predominantly in brain. However, the function of SALL2/Msal-2 still needs to be determined.

Townes-Brocks syndrome and renal dysplasia: a novel mutation in the SALL1 gene

A 14-year-old African-American boy had chronic renal failure and Townes-Brocks syndrome (TBS). There were no affected family members. Features were imperforate anus, rectoperineal fistula, triphalangeal thumb, bifid thumb, rocker bottom feet, bilateral ear tags, satyr ear, sensorineural hearing loss, hypospadias, bilateral renal hypoplasia, and progressive chronic renal failure. Renal and urological anomalies in TBS include renal hypoplasia, renal dysplasia, unilateral renal agenesis, horseshoe kidney, posterior urethral valves, uretero-vesical reflux, and meatal stenosis. TBS is caused by a dominantly inherited defect in the gene encoding the SALL1 putative transcription factor, a protein possibly required for urological, renal, limb, ear, brain, and liver development. This patient had a novel mutation in this gene. The extent of renal involvement in patients with TBS should be evaluated for optimum treatment and prediction of prognosis.

SALL3, a new member of the human spalt-like gene family, maps to 18q23

spalt (sal) of Drosophila melanogaster is an important developmental regulator gene and encodes a zinc finger protein of unusual but characteristic structure. Two human sal-like genes have been isolated so far, SALL1 on chromosome 16q12.1 and SALL2 on chromosome 14q11.1-q12.1. Truncating mutations of SALL1 have been shown to cause Townes-Brocks syndrome and are thought to result in SALL1 haploinsufficiency. Sequence comparison of SALL1 to the related genes Msal in mouse and Xsal-1 in Xenopus laevis suggested that SALL1 was not the human orthologue of Msal and Xsal-1. By database searching and genomic cloning, we isolated an EST and a corresponding human cosmid clone, which contain coding sequence of a human gene highly similar to mouse Msal. This gene, named SALL3, was found to be expressed in different regions of human fetal brain and in different adult human tissues. The chromosomal localization of SALL3 at 18q23 suggests that haploinsufficiency of this gene might contribute to the phenotype of patients with 18q deletion syndrome.