The emotional well-being of parents with children at genetic risk for type 1 diabetes before and during participation in the POInT-study

INTRODUCTION

This study examined the emotional impact that parents experience when confronted with an increased genetic risk of type 1 diabetes (T1D) in their child. Population-based screening of neonates for genetic risk of chronic disease carries the risk of increased emotional burden for parents.

METHODS

Information was collected using a well-being questionnaire for parents of infants identified as having an increased risk for T1D in a multinational research study. Parents were asked to complete this questionnaire after they were told their child had an increased risk for T1D (Freder1k-study) and at several time points during an intervention study (POInT-study), where oral insulin was administered daily.

RESULTS

Data were collected from 2595 parents of 1371 children across five countries. Panic-related anxiety symptoms were reported by only 4.9% after hearing about their child having an increased risk. Symptoms of depression were limited to 19.4% of the parents at the result-communication visit and declined over time during the intervention study. When thinking about their child's risk for developing T1D (disease-specific anxiety), 47.2% worried, felt nervous and tense. Mothers and parents with a first-degree relative (FDR) with T1D reported more symptoms of depression and disease-specific anxiety (p < 0.001) than fathers and parents without a FDR.

CONCLUSION

Overall, symptoms of depression and panic-related anxiety are comparable with the German population. When asked about their child's risk for T1D during the intervention study, some parents reported disease-specific anxiety, which should be kept in mind when considering population-based screening. As certain subgroups are more prone, it will be important to continue psychological screening and, when necessary, to provide support by an experienced, multidisciplinary team.

Pik3ca mutations significantly enhance the growth of SHH medulloblastoma and lead to metastatic tumour growth in a novel mouse model

Medulloblastoma (MB) is the most frequent malignant brain tumour in children with a poor outcome. Divided into four molecular subgroups, MB of the Sonic hedgehog (SHH) subgroup accounts for approximately 25% of the cases and is driven by mutations within components of the SHH pathway, such as its receptors PTCH1 or SMO. A fraction of these cases additionally harbour PIK3CA mutations, the relevance of which is so far unknown. To unravel the role of Pik3ca mutations alone or in combination with a constitutively activated SHH signalling pathway, transgenic mice were used. These mice show mutated variants within Smo, Ptch1 or Pik3ca genes in cerebellar granule neuron precursors, which represent the cellular origin of SHH MB. Our results show that Pik3ca mutations alone are insufficient to cause developmental alterations or to initiate MB. However, they significantly accelerate the growth of Shh MB, induce tumour spread throughout the cerebrospinal fluid, and result in lower survival rates of mice with a double Pik3caH1047R/SmoM2 or Pik3caH1047R/Ptch1 mutation. Therefore, PIK3CA mutations in SHH MB may represent a therapeutic target for first and second line combination treatments.

Identification of infants with increased type 1 diabetes genetic risk for enrollment into Primary Prevention Trials-GPPAD-02 study design and first results

Primary prevention of type 1 diabetes (T1D) requires intervention in genetically at-risk infants. The Global Platform for the Prevention of Autoimmune Diabetes (GPPAD) has established a screening program, GPPAD-02, that identifies infants with a genetic high risk of T1D, enrolls these into primary prevention trials, and follows the children for beta-cell autoantibodies and diabetes. Genetic testing is offered either at delivery, together with the regular newborn testing, or at a newborn health care visits before the age of 5 months in regions of Germany (Bavaria, Saxony, Lower Saxony), UK (Oxford), Poland (Warsaw), Belgium (Leuven), and Sweden (Region Skåne). Seven clinical centers will screen around 330 000 infants. Using a genetic score based on 46 T1D susceptibility single-nucleotide polymorphisms (SNPs) or three SNPS and a first-degree family history for T1D, infants with a high (>10%) genetic risk for developing multiple beta-cell autoantibodies by the age of 6 years are identified. Screening from October 2017 to December 2018 was performed in 50 669 infants. The prevalence of high genetic risk for T1D in these infants was 1.1%. Infants with high genetic risk for T1D are followed up and offered to participate in a randomized controlled trial aiming to prevent beta-cell autoimmunity and T1D by tolerance induction with oral insulin. The GPPAD-02 study provides a unique path to primary prevention of beta-cell autoimmunity in the general population. The eventual benefit to the community, if successful, will be a reduction in the number of children developing beta-cell autoimmunity and T1D.

TCF4 (E2-2) harbors tumor suppressive functions in SHH medulloblastoma

The TCF4 gene encodes for the basic helix-loop-helix transcription factor 4 (TCF4), which plays an important role in the development of the central nervous system (CNS). Haploinsufficiency of TCF4 was found to cause Pitt-Hopkins syndrome (PTHS), a severe neurodevelopmental disorder. Recently, the screening of a large cohort of medulloblastoma (MB), a highly aggressive embryonal brain tumor, revealed almost 20% of adult patients with MB of the Sonic hedgehog (SHH) subtype carrying somatic TCF4 mutations. Interestingly, many of these mutations have previously been detected as germline mutations in patients with PTHS. We show here that overexpression of wild-type TCF4 in vitro significantly suppresses cell proliferation in MB cells, whereas mutant TCF4 proteins do not to the same extent. Furthermore, RNA sequencing revealed significant upregulation of multiple well-known tumor suppressors upon expression of wild-type TCF4. In vivo, a prenatal knockout of Tcf4 in mice caused a significant increase in apoptosis accompanied by a decreased proliferation and failed migration of cerebellar granule neuron precursor cells (CGNP), which are thought to be the cells of origin for SHH MB. In contrast, postnatal in vitro and in vivo knockouts of Tcf4 with and without an additional constitutive activation of the SHH pathway led to significantly increased proliferation of CGNP or MB cells. Finally, publicly available data from human MB show that relatively low expression levels of TCF4 significantly correlate with a worse clinical outcome. These results not only point to time-specific roles of Tcf4 during cerebellar development but also suggest a functional linkage between TCF4 mutations and the formation of SHH MB, proposing that TCF4 acts as a tumor suppressor during postnatal stages of cerebellar development.

Opposing Effects of CREBBP Mutations Govern the Phenotype of Rubinstein-Taybi Syndrome and Adult SHH Medulloblastoma

Recurrent mutations in chromatin modifiers are specifically prevalent in adolescent or adult patients with Sonic hedgehog-associated medulloblastoma (SHH MB). Here, we report that mutations in the acetyltransferase CREBBP have opposing effects during the development of the cerebellum, the primary site of origin of SHH MB. Our data reveal that loss of Crebbp in cerebellar granule neuron progenitors (GNPs) during embryonic development of mice compromises GNP development, in part by downregulation of brain-derived neurotrophic factor (Bdnf). Interestingly, concomitant cerebellar hypoplasia was also observed in patients with Rubinstein-Taybi syndrome, a congenital disorder caused by germline mutations of CREBBP. By contrast, loss of Crebbp in GNPs during postnatal development synergizes with oncogenic activation of SHH signaling to drive MB growth, thereby explaining the enrichment of somatic CREBBP mutations in SHH MB of adult patients. Together, our data provide insights into time-sensitive consequences of CREBBP mutations and corresponding associations with human diseases.

Characterization of pancreatic glucagon-producing tumors and pituitary gland tumors in transgenic mice overexpressing MYCN in hGFAP-positive cells

Amplification or overexpression of MYCN is involved in development and maintenance of multiple malignancies. A subset of these tumors originates from neural precursors, including the most aggressive forms of the childhood tumors, neuroblastoma and medulloblastoma. In order to model the spectrum of MYCN-driven neoplasms in mice, we transgenically overexpressed MYCN under the control of the human GFAP-promoter that, among other targets, drives expression in neural progenitor cells. However, LSL-MYCN;hGFAP-Cre double transgenic mice did neither develop neural crest tumors nor tumors of the central nervous system, but presented with neuroendocrine tumors of the pancreas and, less frequently, the pituitary gland. Pituitary tumors expressed chromogranin A and closely resembled human pituitary adenomas. Pancreatic tumors strongly produced and secreted glucagon, suggesting that they derived from glucagon- and GFAP-positive islet cells. Interestingly, 3 out of 9 human pancreatic neuroendocrine tumors expressed MYCN, supporting the similarity of the mouse tumors to the human system. Serial transplantations of mouse tumor cells into immunocompromised mice confirmed their fully transformed phenotype. MYCN-directed treatment by AuroraA- or Brd4-inhibitors resulted in significantly decreased cell proliferation in vitro and reduced tumor growth in vivo. In summary, we provide a novel mouse model for neuroendocrine tumors of the pancreas and pituitary gland that is dependent on MYCN expression and that may help to evaluate MYCN-directed therapies.