We identified loss-of-function mutations in ATP6V0A2, encoding the a2 subunit of the V-type H+ ATPase, in several families with autosomal recessive cutis laxa type II or wrinkly skin syndrome. The mutations result in abnormal glycosylation of serum proteins (CDG-II) and cause an impairment of Golgi trafficking in fibroblasts from affected individuals. These results indicate that the a2 subunit of the proton pump has an important role in Golgi function.

The conserved oligomeric Golgi (COG) complex is a hetero-octameric complex essential for normal glycosylation and intra-Golgi transport. An increasing number of congenital disorder of glycosylation type II (CDG-II) mutations are found in COG subunits indicating its importance in glycosylation. We report a new CDG-II patient harbouring a p.R729W missense mutation in COG4 combined with a submicroscopical deletion. The resulting downregulation of COG4 expression additionally affects expression or stability of other lobe A subunits. Despite this, full complex formation was maintained albeit to a lower extent as shown by glycerol gradient centrifugation. Moreover, our data indicate that subunits are present in a cytosolic pool and full complex formation assists tethering preceding membrane fusion. By extending this study to four other known COG-deficient patients, we now present the first comparative analysis on defects in transport, glycosylation and Golgi ultrastructure in these patients. The observed structural and biochemical abnormalities correlate with the severity of the mutation, with the COG4 mutant being the mildest. All together our results indicate that intact COG complexes are required to maintain Golgi dynamics and its associated functions. According to the current CDG nomenclature, this newly identified deficiency is designated CDG-IIj.

The hetero-octameric conserved oligomeric Golgi (COG) complex is essential for the structure/function of the Golgi apparatus through regulation of membrane trafficking. Here, we describe a patient with a mild form of a congenital disorder of glycosylation type II (CDG-II), which is caused by a homozygous nonsense mutation in the hCOG8 gene. This leads to a premature stop codon resulting in a truncated Cog8 subunit lacking the 76 C-terminal amino acids. Mass spectrometric analysis of the N- and O-glycan structures identified a mild sialylation deficiency. We showed that the molecular basis of this defect in N- and O-glycosylation is caused by the disruption of the Cog1-Cog8 interaction due to truncation. As a result, Cog1 deficiency accompanies the Cog8 deficiency, preventing assembly of the intact, stable complex and resulting in the appearance of smaller subcomplexes. Moreover, levels of beta1,4-galactosytransferase were significantly reduced. The defects in O-glycosylation could be fully restored by transfecting the patient's fibroblasts with full-length Cog8. The Cog8 defect described here represents a novel type of CDG-II, which we propose to name as CDG-IIh or CDG caused by Cog8 deficiency (CDG-II/Cog8).

Protein glycosylation is one of the major biosynthetic functions occurring in the endoplasmic reticulum and Golgi compartments. It requires an amazing number of enzymes, chaperones, lectins and transporters whose actions delicately secure the fidelity of glycan structures. Over the past 30 years, glycobiologists hammered that glycan structures are not mere decorative elements but serve crucial cellular functions. This becomes dramatically illustrated by a group of mostly severe, inherited human disorders named congenital disorders of glycosylation (CDG). To date, many types of CDG have been defined genetically and most of the time the defects impair the biosynthesis, transfer and remodeling of N-glycans. Recently, the identification of the several types of CDG caused by deficiencies in the conserved oligomeric Golgi (COG) complex, a complex involved in vesicular Golgi trafficking, expanded the field of CDG but also brought novel insights in glycosylation. The molecular mechanisms underlying the complex pathway of N-glycosylation in the Golgi are far from understood. The availability of COG-deficient CDG patients and patients' cells offered a new way to study how COG, and its different subunits, could influence the Golgi N-glycosylation machinery and localization. This review summarizes the recent findings on the implication of COG in Golgi glycosylation. It highlights the need for a dynamic, finely tuned balance between anterograde and retrograde trafficking for the correct localization of Golgi enzymes to assure the stepwise maturation of N-glycan chains.

We describe two patients with a cerebrocostomandibular-like syndrome and a novel mutation in conserved oligomeric Golgi (COG) subunit 1, one of the subunits of the conserved oligomeric Golgi complex. This hetero-octameric protein complex is involved in retrograde vesicular trafficking and glycosylation. We identified in both patients an intronic mutation, c.1070+5G>A, that disrupts a splice donor site and leads to skipping of exon 6, a frameshift and a premature stopcodon in exon 7. Real-time reverse transcriptase polymerase chain reaction showed in the first patient only 3% of normal transcript when compared with control. A delay in retrograde trafficking could be demonstrated by Brefeldin A treatment of this patient's fibroblasts. The costovertebral dysplasia of the two patients has been described in cerebrocostomandibular syndrome (CCMS), but also in cerebrofaciothoracic dysplasia and spondylocostal dysostosis. CCMS itself is heterogeneous because both autosomal dominant and autosomal recessive inheritance has been described. We anticipate further genetic heterogeneity because no mutations in COG1 were found in two additional patients with a CCMS.

BackgroundEverolimus in combination with exemestane is indicated for the treatment of hormone receptor-positive, HER 2-neg endocrine resistant advanced breast cancer in postmenopausal women. This study investigated treatment adherence, tolerability, satisfaction and efficacy. MethodsA prospective, non-interventional, non-controlled, multicentric observational study assessed adherence by means of a validated questionnaire (‘Morisky Medication Adherence Scale’) and ‘Medication Event Monitoring System’ (MEMS®) data. The level of adherence was calculated per patient as percentage of days on which the medicine was taken as prescribed during the total treatment period, referred to as ‘unadjusted adherence rate’ (UAR). Second, MEMS® data were adjusted for treatment interruptions according to the CRF and questionnaire data, approved by the treating physician (‘adjusted adherence rate’ (AAR)). Successful adherence was defined as ≥ 95% – ≤ 105%. Validated questionnaires (‘Patient Satisfaction with Cancer Treatment Education’, ‘Cancer Treatment Satisfaction Questionnaire’ (CTSQ) and ‘Functional Assessment of Cancer Therapy – General’ (FACT-G) were used to report patients experience and satisfaction with the treatment and perceived care, questioned at initial visit and after approximately 1, 3, 6 and 12 months. The efficacy was primary analyzed through progression free survival (PFS). ResultsBetween Dec 2015 and Nov 2017, a total of 58 women (median age 65 yrs) from 7 oncology centers were included after a mean of 34m ± 36.9 (SD) of being diagnosed with stage IV disease; most (62.1%) had ≥3 organs involved and 84.5% had ≥2 prior metastatic treatment lines. The mean follow-up duration was 185.5 ± 100.0 days. The mean UAR for exemestane, everolimus and the combination were 92.9 %, 84.8 % and 81.7 % respectively. For everolimus and the combination therapy these rates differ significantly from the mean AAR, with p < 0.05 (see table 1). For the AAR of the combination therapy, 13.8 % of the patients showed optimal adherence (100 %). Six patients (10.3%) interrupted their treatment with exemestane with a mean time of treatment pause of 34.3 ± 19.1 days. The treatment with everolimus was interrupted by 36 (62.1%), with a mean interruption time of 24.3 ± 16.5 days, which corresponds with a mean of 19.6 % ± 17.6% of the total follow-up duration. Some patients interrupted their treatment multiple times. The most common side effect was mucositis (n=26 at 1 month, of whom 8 patients grade 3 and 15 patients grade 2)). Six (10.4 %) of the 58 patients stopped treatment with everolimus and exemestane due to side effects. The median PFS was 170 days. With regard to quality of life, patients scored lowest on emotional and functional well-being. However, there were no significant differences measured for the mean FACT-G score between Day0, M1 and M3 (P = 0.273). Also, patients scored overall low on the ‘CTSQ’. Conclusion Despite close monitoring and preventive measures to overcome side effects, adherence to everolimus and exemestane was rather low. Many patients needed to interrupt the treatment due to side effects; treatment is perceived as intensive. Nevertheless, median PFS is 170 days, even when used late in the therapeutic journey of breast cancer patients. Table 1. UAR and AAR for Exemestane, Everolimus and the combinationExemestaneEverolimusCombination therapyUAR (%)mean ± SD92.97 ± 13.1784.86 ± 19.4081.74 ± 20.98AAR (%)mean ± SD93.07 ± 13.1491.81 ± 15.0487.55 ± 18.17Significance differenceP-value0.277< 0.001< 0.001 Citation Format: Veerle Foulon, Carrie Visser, Sandra De Coster, Lise-Marie Kinnaer, Ellen Reynders, Anne Deblander, Patrick Berteloot, Kevin Punie, Hans Wildiers, Véronique Cocquyt, Hannelore Denys, Ahmad Awada, Eric Strobbe, Andrea Gombos, Isabelle Spoormans, Ximena Elzo-Kraemer, Christof Vulsteke, Marleen Borms, Philip Debruyne, Wim Wynendaele, Patrick Neven. Adherence to and patient satisfaction with the combination therapy of exemestane and everolimus in postmenopausal women with HR+ HER2- advanced breast cancer: Results from the IPSOC-mamma study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS9-06.