Truncating Mutation In Exon Research Articles

PPM1D activity promotes cellular transformation by preventing senescence and cell death

Cell cycle checkpoints, oncogene-induced senescence and programmed cell death represent intrinsic barriers to tumorigenesis. Protein phosphatase magnesium-dependent 1 (PPM1D) is a negative regulator of the tumour suppressor p53 and has been implicated in termination of the DNA damage response. Here, we addressed the consequences of increased PPM1D activity resulting from the gain-of-function truncating mutations in exon 6 of the PPM1D. We show that while control cells permanently exit the cell cycle and reside in senescence in the presence of DNA damage caused by ionising radiation or replication stress induced by the active RAS oncogene, RPE1-hTERT and BJ-hTERT cells carrying the truncated PPM1D continue proliferation in the presence of DNA damage, form micronuclei and accumulate genomic rearrangements revealed by karyotyping. Further, we show that increased PPM1D activity promotes cell growth in the soft agar and formation of tumours in xenograft models. Finally, expression profiling of the transformed clones revealed dysregulation of several oncogenic and tumour suppressor pathways. Our data support the oncogenic potential of PPM1D in the context of exposure to ionising radiation and oncogene-induced replication stress.

Novel Exon-Skipping Therapeutic Approach for the DMD Gene Based on Asymptomatic Deletions of Exon 49.

Exon skipping is a promising therapeutic approach. One important condition for this approach is that the exon-skipped form of the gene can at least partially perform the required function and lead to improvement of the phenotype. It is therefore critical to identify the exons that can be skipped without a significant deleterious effect on the protein function. Pathogenic variants in the DMD gene are responsible for Duchenne muscular dystrophy (DMD). We report for the first time a deletion of the in-frame exon 49 associated with a strikingly normal muscular phenotype. Based on this observation, and on previously known therapeutic approaches using exon skipping in DMD for other single exons, we aimed to extend the clinical use of exon skipping for patients carrying truncating mutations in exon 49. We first determined the precise genomic position of the exon 49 deletion in our patients. We then demonstrated the feasibility of skipping exon 49 using an in vitro AON (antisense oligonucleotide) approach in human myotubes carrying a truncating pathogenic variant as well as in healthy ones. This work is a proof of concept aiming to expand exon-skipping approaches for DMD exon 49.

Truncated PPM1D Prevents Apoptosis in the Murine Thymus and Promotes Ionizing Radiation-Induced Lymphoma.

Genome integrity is protected by the cell-cycle checkpoints that prevent cell proliferation in the presence of DNA damage and allow time for DNA repair. The transient checkpoint arrest together with cellular senescence represent an intrinsic barrier to tumorigenesis. Tumor suppressor p53 is an integral part of the checkpoints and its inactivating mutations promote cancer growth. Protein phosphatase magnesium-dependent 1 (PPM1D) is a negative regulator of p53. Although its loss impairs recovery from the G2 checkpoint and promotes induction of senescence, amplification of the PPM1D locus or gain-of-function truncating mutations of PPM1D occur in various cancers. Here we used a transgenic mouse model carrying a truncating mutation in exon 6 of PPM1D (Ppm1dT). As with human cell lines, we found that the truncated PPM1D was present at high levels in the mouse thymus. Truncated PPM1D did not affect differentiation of T-cells in the thymus but it impaired their response to ionizing radiation (IR). Thymocytes in Ppm1dT/+ mice did not arrest in the checkpoint and continued to proliferate despite the presence of DNA damage. In addition, we observed a decreased level of apoptosis in the thymi of Ppm1dT/+ mice. Moreover, the frequency of the IR-induced T-cell lymphomas increased in Ppm1dT/+Trp53+/− mice resulting in decreased survival. We conclude that truncated PPM1D partially suppresses the p53 pathway in the mouse thymus and potentiates tumor formation under the condition of a partial loss of p53 function.

Novel STAG3 mutations in a Caucasian family with primary ovarian insufficiency.

Primary ovarian insufficiency (POI) affects ~ 1-3, 7% of women under forty and is a public health problem. Most causes are unknown, but an increasing number of genetic causes have been identified recently. The identification of such causes is essential for genetic and therapeutic counseling in patients and their families. We performed whole exome sequencing in two Caucasian sisters displaying non syndromic POI and their unaffected mother. We identified two novel pathogenic variants in STAG3 encoding a meiosis-specific subunit of the cohesin ring, which ensures correct sister chromatid cohesion: a c.3052delC truncating mutation in exon 28 yielding p.Arg1018Aspfs*14, and a c.659T > G substitution in exon seven yielding p.Leu220Arg. Leu220, highly conserved throughout species, belongs to the STAG domain conserved with other mitotic subunits of the cohesion complex STAG1 and 2. In silico analysis reveals that this substitution markedly impacts the structure of this domain. The truncation removes the last 206 C-terminal residues, not conserved in STAG1 and 2, supporting an important specific role in STAG3, especially meiosis. This is the first occurrence of STAG3 mutations in a Caucasian family. Very little is known about the function of STAG proteins domains. The "knock out-like" phenotype described here supports the crucial role of a single residue in the STAG domain and of the C-terminal region in STAG3 function. In conclusion, this observation shows the necessity to perform the genetic study of POI worldwide including STAG3. This could lead to appropriate genetic counseling and long term follow-up since these patients may develop ovarian tumors.

A case report of reversible generalized seizures in a patient with Waardenburg syndrome associated with a novel nonsense mutation in the penultimate exon of SOX10

BackgroundWaardenburg syndrome type 1 (WS1) can be distinguished from Waardenburg syndrome type 2 (WS2) by the presence of dystopia canthorum. About 96% of WS1 are due to PAX3 mutations, and SOX10 mutations have been reported in 15% of WS2.Case presentationThis report describes a patient with WS1 who harbored a novel SOX10 nonsense mutation (c.652G > T, p.G218*) in exon 3 which is the penultimate exon. The patient had mild prodromal neurological symptoms that were followed by severe attacks of generalized seizures associated with delayed myelination of the brain. The immature myelination recovered later and the neurological symptoms could be improved. This is the first truncating mutation in exon 3 of SOX10 that is associated with neurological symptoms in Waardenburg syndrome. Previous studies reported that the neurological symptoms that associate with WS are congenital and irreversible. These findings suggest that the reversible neurological phenotype may be associated with the nonsense mutation in exon 3 of SOX10.ConclusionsWhen patients of WS show mild prodromal neurological symptoms, the clinician should be aware of the possibility that severe attacks of generalized seizures may follow, which may be associated with the truncating mutation in exon 3 of SOX10.

Two de novo novel mutations in one SHANK3 allele in a patient with autism and moderate intellectual disability.

SHANK3 encodes for a scaffolding protein that links neurotransmitter receptors to the cytoskeleton and is enriched in postsynaptic densities of excitatory synapses. Deletions or mutations in one copy of the SHANK3 gene cause Phelan-McDermid syndrome, also called 22q13.3 deletion syndrome, a neurodevelopmental disorder with common features including global developmental delay, absent to severely impaired language, autistic behavior, and minor dysmorphic features. By whole exome sequencing, we identified two de novo novel variants including one frameshift pathogenic variant and one missense variant of unknown significance in a 14-year-old boy with delayed motor milestones, delayed language acquisition, autism, intellectual disability, ataxia, progressively worsening spasticity of the lower extremities, dysmorphic features, short stature, microcephaly, failure to thrive, chronic constipation, intrauterine growth restriction, and bilateral inguinal hernias. Both changes are within the CpG island in exon 21, separated by a 375 bp sequence. Next generation sequencing of PCR products revealed that the two variants are most frequently associated with each other. Sanger sequencing of the cloned PCR products further confirmed that both changes were on a single allele. The clinical presentation in this individual is consistent with other patients with a truncating mutation in exon 21, suggesting that the missense change contributes none or minimally to the phenotypes. This is the first report of two de novo mutations in one SHANK3 allele.

Prevalence of Congenital Ocular Anomalies among Children with Genetic Disorders: An Egyptian Study

ABSTRACTPurpose: To assess the pattern and frequency of occurrence of ocular anomalies among other genetic disorders in Egypt. Methods: This is a cross-sectional study of 2500 cases presenting with genetic disorders. Cases were recruited from the clinical genetics department of the National Research Centre (NRC) over a four-year period between January 2011 and December 2014. Ophthalmological examination of the cases was performed in the pediatric ophthalmology department of Cairo University Hospitals. Results: Out of 2500 cases with congenital disorders, 2.4% suffered one or more ocular anomalies with a male to female ratio of 1.7:1. Consanguinity was reported in 76.7% and family history was positive in 35% of ocular cases. The most common ocular anomalies were congenital cataract, retinal dystrophies, glaucoma, and retinoblastoma in order of frequency. Chromosomal aberrations were detected in two retinoblastoma cases and in one case of charge association with cataract and iris coloboma. A truncating mutation in exon 8 of OCRL1 was reported in a case of Lowe syndrome with cataract. A total of 51.7% of ocular cases were non-isolated (associated with other genetic disorders). Conclusion: In Egypt, ocular genetic disorders are not uncommon among other genetic disorders. Consanguinity is high, suggesting high incidence of autosomal recessive inheritance of genetic disorders with an ocular component. Proper systemic assessment of all cases with ocular anomalies is a necessity due to the high percentage of non-isolated ocular anomalies. Genetic counseling of parents would help in reducing recurrence rates through prenatal diagnosis whenever possible.

NKL homeobox gene MSX1 acts like a tumor suppressor in NK-cell leukemia.

NKL homeobox gene MSX1 is physiologically expressed in lymphoid progenitors and subsequently downregulated in developing T- and B-cells. In contrast, elevated expression levels of MSX1 persist in mature natural killer (NK)-cells, indicating a functional role in this compartment. While T-cell acute lymphoblastic leukemia (T-ALL) subsets exhibit aberrant overexpression of MSX1, we show here that in malignant NK-cells the level of MSX1 transcripts is aberrantly downregulated. Chromosomal deletions at 4p16 hosting the MSX1 locus have been described in NK-cell leukemia patients. However, NK-cell lines analyzed here showed normal MSX1 gene configurations, indicating that this aberration might be uncommon. To identify alternative MSX1 regulatory mechanisms we compared expression profiling data of primary normal NK-cells and malignant NK-cell lines. This procedure revealed several deregulated genes including overexpressed IRF4, MIR155HG and MIR17HG and downregulated AUTS2, EP300, GATA3 and HHEX. As shown recently, chromatin-modulator AUTS2 is overexpressed in T-ALL subsets where it mediates aberrant transcriptional activation of MSX1. Here, our data demonstrate that in malignant NK-cell lines AUTS2 performed MSX1 activation as well, but in accordance with downregulated MSX1 transcription therein we detected reduced AUTS2 expression, a small genomic deletion at 7q11 removing exons 3 and 4, and truncating mutations in exon 1. Moreover, genomic profiling and chromosomal analyses of NK-cell lines demonstrated amplification of IRF4 at 6p25 and deletion of PRDM1 at 6q21, highlighting their potential oncogenic impact. Functional analyses performed via knockdown or forced expression of these genes revealed regulatory network disturbances effecting downregulation of MSX1 which may underlie malignant development in NK-cells.

De Novo GMNN Mutations Cause Autosomal-Dominant Primordial Dwarfism Associated with Meier-Gorlin Syndrome

Meier-Gorlin syndrome (MGS) is a genetically heterogeneous primordial dwarfism syndrome known to be caused by biallelic loss-of-function mutations in one of five genes encoding pre-replication complex proteins: ORC1, ORC4, ORC6, CDT1, and CDC6. Mutations in these genes cause disruption of the origin of DNA replication initiation. To date, only an autosomal-recessive inheritance pattern has been described in individuals with this disorder, with a molecular etiology established in about three-fourths of cases. Here, we report three subjects with MGS and de novo heterozygous mutations in the 5' end of GMNN, encoding the DNA replication inhibitor geminin. We identified two truncating mutations in exon 2 (the 1(st) coding exon), c.16A>T (p.Lys6(∗)) and c.35_38delTCAA (p.Ile12Lysfs(∗)4), and one missense mutation, c.50A>G (p.Lys17Arg), affecting the second-to-last nucleotide of exon 2 and possibly RNA splicing. Geminin is present during the S, G2, and M phases of the cell cycle and is degraded during the metaphase-anaphase transition by the anaphase-promoting complex (APC), which recognizes the destruction box sequence near the 5' end of the geminin protein. All three GMNN mutations identified alter sites 5' to residue Met28 of the protein, which is located within the destruction box. We present data supporting a gain-of-function mechanism, in which the GMNN mutations result in proteins lacking the destruction box and hence increased protein stability and prolonged inhibition of replication leading to autosomal-dominant MGS.

Mutations in CACNA2D4 Cause Distinctive Retinal Dysfunction in Humans

CACNA2D4 (NM_172364) encodes the α2δ4 subunit of the photoreceptor voltage-gated calcium channels (Cav1.4), which modulate glutamate release from the photoreceptors to the bipolar cells. 1 Dolphin A.C. The α2δ subunits of voltage-gated calcium channels. Biochim Biophys Acta. 2013; 1828: 1541-1549 Crossref PubMed Scopus (143) Google Scholar CACNA2D4 mutations have been associated with a rare recessive retinal cone dystrophy (RCD4, OMIM #610478), 2 Wycisk K.A. Zeitz C. Feil S. et al. Mutation in the auxiliary calcium-channel subunit CACNA2D4 causes autosomal recessive cone dystrophy. Am J Hum Genet. 2006; 79: 973-977 Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar first described in 2 adult siblings with a homozygous truncating mutation in exon 25 of CACNA2D4: c.[2406C>A] (p.[Tyr802*]) associated with mildly reduced visual acuity (VA), photophobia, foveal pigment mottling, an electronegative scotopic electroretinogram (ERG) and markedly subnormal cone responses. 2 Wycisk K.A. Zeitz C. Feil S. et al. Mutation in the auxiliary calcium-channel subunit CACNA2D4 causes autosomal recessive cone dystrophy. Am J Hum Genet. 2006; 79: 973-977 Abstract Full Text Full Text PDF PubMed Scopus (117) Google Scholar The second report described a homozygous deletion of exons 17-26 of CACNA2D4 associated with mildly reduced VA, photophobia, normal retinal imaging, normal scotopic ERG, and mildly reduced cone responses (Vincent A, et al. Non-truncating homozygous deletion in CACNA2D4 mimicking oligocone trichromacy. Poster, ARVO 2014, Orlando, FL). The third report suggested a cone–rod dystrophy caused by a homozygous mutation: c.[2120G>A], (p.[Arg707His]). 3 Huang X.F. Huang F. Wu K.C. et al. Genotype-phenotype correlation and mutation spectrum in a large cohort of patients with inherited retinal dystrophy revealed by next-generation sequencing. Genet Med. 2015; 17: 271-278 Abstract Full Text Full Text PDF PubMed Scopus (150) Google Scholar

Our panel of experts highlight the most important research articles across the spectrum of topics relevant to the field of CNS oncology

Our panel of experts highlight the most important research articles across the spectrum of topics relevant to the field of CNS oncology

Hypomorphic NOTCH3 mutation in an Italian family with CADASIL features

The cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is because of NOTCH3 mutations affecting the number of cysteine residues. In this view, the role of atypical NOTCH3 mutations is still debated. Therefore, we investigated a family carrying a NOTCH3 nonsense mutation, with dominantly inherited recurrent cerebrovascular disorders. Among 7 family members, 4 received a clinical diagnosis of CADASIL. A heterozygous truncating mutation in exon 3 (c.307C>T, p.Arg103X) was found in the 4 clinically affected subjects and in one 27-year old lady, only complaining of migraine with aura. Magnetic resonance imaging scans found typical signs of small-vessel disease in the 4 affected subjects, supporting the clinical diagnosis. Skin biopsies did not show the typical granular osmiophilic material, but only nonspecific signs of vascular damage, resembling those previously described in Notch3 knockout mice. Interestingly, messenger RNA (mRNA) analysis supports the hypothesis of an atypical NOTCH3 mutation, suggesting a nonsense-mediated mRNA decay. In conclusion, the present study broadens the spectrum of CADASIL mutations, and, therefore, opens new insights about Notch3 signaling.

Clinical and Molecular Study of the Extracellular Matrix Protein 1 Gene in a Spanish Family with Lipoid Proteinosis

BackgroundLipoid proteinosis (LP) is a rare autosomal recessive disorder characterized by a hoarse voice, variable scarring, and infiltration of the skin and mucosa. This disease is associated with mutations of the gene encoding extracellular matrix protein 1 (ECM1).Case ReportThis was a clinical and molecular study of a new case of LP with a severe phenotype. A 35-year-old female born to nonconsanguineous parents developed dermatological and extracutaneous symptoms in her 9th month of life. The neurological abnormalities of the disease began to appear at the age of 19 years. Computed tomography revealed cranial calcifications.ConclusionsThe diagnosis of LP was confirmed by histopathological findings and direct sequencing of ECM1. A new homozygous nonsense mutation was identified in exon 7 of ECM1, c.1076G>A (p.Trp359*). This mutation was not detected in 106 chromosomes of healthy individuals with a similar demographic origin. Microsatellite markers around ECM1 were used to construct the haplotype in both the parents and the patient. Reports on genotype-phenotype correlations in LP point to a milder phenotype in carriers of missense mutations in the Ecm1a isoform, whereas mutations in the Ecm1b isoform are thought to be associated with more severe phenotypes. The present findings in a Spanish patient carrying a truncating mutation in exon 7 revealed complete dermatological and neurological manifestations.

Identification and expression analysis of a novel intragenic EFNB1 mutation causing craniofrontonasal syndrome

Craniofrontonasal syndrome (CFNS) is an X-linked disorder caused by mutations in the EFNB1 gene and characterized by distinctive craniofacial and digital malformations. In contrast with most X-linked traits, female patients with CFNS display a more severe phenotype than males. In this report, the clinical, molecular and RNA expression analyses of a female subject with CFNS are described. A novel c.445_449delGAGGG deletion in exon 3 of EFNB1 was demonstrated in this patient. To assess the effect of this novel mutation at the transcript level, the expression of EFNB1 mRNA was studied by quantitative RT-PCR. To our knowledge, this is the first time that an EFNB1 transcript carrying a truncating mutation in exon 3 is demonstrated to undergo degradation by nonsense-mediated mRNA decay. Our results expand the mutational spectrum of CFNS and add to the functional consequences of truncating EFNB1 mutations.

“Clinical consequences in truncating mutations in exon 34 of NOTCH2: report of six patients with Hajdu‐Cheney syndrome and a patient with serpentine fibula polycystic kidney syndrome” Am J Med Genet. 161:518–526, 2013

We have recently discovered a miscounted error which was reported as mutated nucleotide sequence. We confirmed the data and correct the error as below. Document Page 525 (left column), line 10: c.6443T > G Table I (page 524) Patient 5–7's nucleotide (line 3, column 6–8): 6443 T > G The authors regret the errors.

Clinical consequences in truncating mutations in exon 34 of NOTCH2: Report of six patients with Hajdu–Cheney syndrome and a patient with serpentine fibula polycystic kidney syndrome

It is debatable whether Hajdu-Cheney syndrome (HCS) and serpentine fibula-polycystic kidney syndrome (SFPKS) represent a single clinical entity with a variable degree of expression or two different entities, because both disorders share common clinical and radiological manifestations, including similar craniofacial characteristics, and defective bone mineralization. Since it was shown that heterozygous truncating mutations in NOTCH2 are responsible for both HCS and SFPKS, 37 patients with HCS and four patients with SFPKS are reported. To elucidate the clinical consequences of NOTCH2 mutations, we present detailed clinical information for seven patients with truncating mutations in exon 34 of NOTCH2, six with HCS and one with SFPKS. In addition, we review all the reported patients whose clinical manifestations are available. We found 13 manifestations including craniofacial features, acroosteolysis, Wormian bones, and osteoporosis in >75% of NOTCH2-positive patients. Acroosteolysis was observed in two patients with SFPKS and bowing fibulae were found in two patients with HCS. These clinical and molecular data would support the notion that HCS and SFPKS are a single disorder.

Characterization of NF1 allele containing two nonsense mutations in exon 37 that segregates with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disease caused by mutations in the NF1 gene. The mutation rate of NF1 is one of the highest known for human genes and the mutational analysis has revealed a wide variety of changes, a significant proportion of which affect normal pre-mRNA splicing. Here, we describe two truncating mutations in exon 37 of NF1, the recurrent c.6792C>A and the novel c.6799C>T change, that occur in cis and segregate with NF1 in a large family. The double mutation induces defective splicing of exon 37 and thus, we performed quantitative comparisons of transcripts harboring single (c.6792C>G or c.6792C>A) and double (c.6792C>A and c.6799C>T) mutations to assess their effects on exon 37 splicing. Skipping of exon 37 was greater and there were fewer mutant full-length transcripts in samples with the double mutation than in those carrying single mutations. Thus, the combination of the c.6792C>A and c.6799C>T mutations augmented exon 37 skipping. These findings suggest that, in addition to the previously described exonic splicing enhancer in the c.6791_6795 region, c.6799 lies within an additional regulatory element that influences the splicing of exon 37.

Autosomal Recessive Retinitis Pigmentosa Caused by Mutations in theMAKGene

To determine the disease expression in autosomal recessive (ar) retinitis pigmentosa (RP) caused by mutations in the MAK (male germ cell-associated kinase) gene. Patients with RP and MAK gene mutations (n = 24; age, 32-77 years at first visit) were studied by ocular examination, perimetry, and optical coherence tomography (OCT). All but one MAK patient were homozygous for an identical truncating mutation in exon 9 and had Ashkenazi Jewish heritage. The carrier frequency of this mutation among 1207 unrelated Ashkenazi control subjects was 1 in 55, making it the most common cause of heritable retinal disease in this population and MAK-associated RP the sixth most common Mendelian disease overall in this group. Visual acuities could be normal into the eighth decade of life. Kinetic fields showed early loss in the superior-temporal quadrant. With more advanced disease, superior and midperipheral function was lost, but the nasal field remained. Only a central island was present at late stages. Pigmentary retinopathy was less prominent in the superior nasal quadrant. Rod-mediated vision was abnormal but detectable in the residual field; all patients had rod>cone dysfunction. Photoreceptor layer thickness was normal centrally but decreased with eccentricity. At the stages studied, there was no evidence of photoreceptor ciliary elongation. The patterns of disease expression in the MAK form of arRP showed some resemblance to patterns described in autosomal dominant RP, especially the form caused by RP1 mutations. The similarity in phenotypes is of interest, considering that there is experimental evidence of interaction between Mak and RP1 in the photoreceptor cilium.

Inactivating Gene Alterations of MHC Class II Transactivator CIITA Are Recurrent in Primary Mediastinal B Cell Lymphoma and Hodgkin Lymphoma

Abstract 437 INTRODUCTION:Escape from immune surveillance has been proposed to play an important role in cancer and in particular in the pathogenesis of a subgroup of lymphomas. Using massively parallel sequencing, we have recently identified recurrent rearrangements of the CIITA gene in classical Hodgkin lymphoma (HL) and primary mediastinal B cell lymphoma (PMBCL) (Steidl et al, Nature 2011). Specifically, a gene fusion in the HL cell line KM-H2, involving the genes CIITA and FLJ27352, suppressed expression of CIITA-regulated MHC class II genes in a dominant-negative manner. Therefore, we sought to further investigate if gene alterations targeting the CIITA locus are recurrent somatic events in HL and PMBCL that lead to loss of gene function and thereby reduce immunogenicity of the malignant cells. PATIENTS AND METHODS: To characterize CIITA gene alterations, we comprehensively studied the cell lines DEV (nodular lymphocyte predominance HL-derived) and KARPAS1106P (PMBCL-derived) by whole-transcriptome paired-end sequencing (RNA-seq) and single nucleotide polymorphism arrays (Affymetrix SNP 6.0). To identify single nucleotide mutations in the CIITA coding sequence we studied additional 7 mediastinal biopsy specimens of PMBCL by RNA-seq. Fluorescence in-situ hybridization (FISH) was used to determine and validate structural and copy number alterations of the CIITA locus. 23 samples of PMBCL, 3 PMBCL-derived cell lines and 9 HL cell lines were studied for mutations and small deletions in CIITA intron 1 by long-range PCR and direct sequencing. CIITA and HLA-DR expression levels were determined by quantitative reverse transcriptase PCR. RESULTS: We identified chromosomal rearrangements affecting both alleles of CIITA in DEV cells resulting in expression of CIITA-PDL2, CIITA-SOCS1 and SOCS1-CIITA fusion transcripts. In KARPAS1106P cells chromosome 16 deletions result in the loss of one entire CIITA allele and partial loss of the other allele. As a consequence, in both cell lines wildtype CIITA and HLA-DR expression was undetectable. Genomic breakpoints within the CIITA rearrangements, together with previously identified translocations, defined a 1.6Kb breakpoint cluster region in CIITA Intron 1. Further analysis of this breakpoint cluster region revealed small intronic deletions in 10 of 23 (43%) PMBCL cases while no such deletions were detected in 18 diffuse large B cell lymphoma and 15 reactive lymph node samples. Furthermore, sequencing revealed multiple deletions ranging from 1–1948 bp and a high incidence of single nucleotide mutations in the breakpoint cluster region of the deleted alleles. The base pair changes were enriched for C to T and G to A transitions over other transitions and transversions, indicative of a somatic hypermutation process. We found significantly lower CIITA expression in cases with CIITA rearrangement and/or small intronic deletions compared to cases without CIITA alterations (p=0.044). RNAseq revealed three cases with non-synonymous coding-sequence mutations including a truncating mutation in exon 4. These changes were somatic in 3 cases with available matching normal DNA. DISCUSSION:CIITA is the target of multiple genomic hits including chromosomal translocation, deletion and coding sequence mutations in HL and PMBCL. In two HL and PMBCL cell lines this leads to complete gene inactivation and loss of HLA class II expression. These data characterize CIITA alterations as a recurrent underlying genomic event of the previously described immunophenotype of reduced HLA class II expression in a subset of PMBCL cases. Our data show that an immune escape mechanism utilized by tumor cells can be directly linked to somatically acquired alterations in cancer genomes. Disclosures:Siebert:Abbott/Vysis: .

Serpentine fibula polycystic kidney syndrome is part of the phenotypic spectrum of Hajdu–Cheney syndrome

Serpentine fibula polycystic kidney syndrome (SFPKS; MIM600330) is a rare skeletal dysplasia that has polycystic kidneys and dysmorphic facies as additional defining phenotypic components. The nosological classification of this disease has been debated as the condition shares features common to other skeletal dysplasias such as Melnick Needles syndrome (MNS; MIM309350) and Hajdu-Cheney Syndrome (HCS; MIM102500). Here, two previously reported cases of SFPKS are presented with emphasis on their phenotypic evolution. With the recent discovery that HCS is caused by mutations in NOTCH2, DNA from the both cases was examined and both were found to have truncating mutations in exon 34 of NOTCH2. The phenotypic evolution of SFPKS and this molecular analysis strongly suggest that SFPKS is part of the phenotypic spectrum of HCS and should no longer be classified as a distinct disease entity.