A qualitative exploration of how to support PrEP adherence among young men who have sex with men

New HIV infections disproportionately affect young men who have sex with men (YMSM). PrEP is effective in preventing HIV acquisition; however, adherence is critical and is often suboptimal among YMSM. Interventions addressing the unique PrEP adherence challenges faced by YMSM are needed. We conducted qualitative interviews with 20 HIV-negative, YMSM (ages 15-24) with a PrEP indication and 11 healthcare professionals to inform adaption of a PrEP adherence intervention (Life-Steps for PrEP) for YMSM. We explored environmental, healthcare, and individual factors influencing uptake, adherence, attitudes, and perspectives (including desired modifications) on the Life-Steps intervention. Interviews were analyzed using content analysis. Of YMSM study participants (mean age 21.6) 55% were White, 15% Hispanic, and 5% Black. Most YMSM were PrEP-experienced (70%). Healthcare professionals (6 prescribers, 1 nurse, 2 health educators, 2 other/unspecified) averaged 6.9 years of experience caring for YMSM. All described stigma as a barrier to PrEP; YMSM expressed concern around being perceived as "risky" and concern about inadvertent PrEP disclosure if family/friends found their medication, or if parental insurance was used. Difficulty with planning for potential adherence challenges were identified by both groups. YMSM highlighted benefits of a nurse-led intervention (i.e., adding "legitimacy"), but stressed need for nonjudgmental, "savvy" interventionists. YMSM expressed a desire for comprehensive YMSM-specific sexual health information. These findings informed modification and expansion of Life-Steps content. Results highlight key potential barriers, many of which center around privacy. Content that addresses PrEP stigma, disclosing PrEP use, navigating insurance, and planning ahead in a nonjudgmental environment by trusted providers emerged as important components of a YMSM-focused delivery of Life-Steps for PrEP.

Utilization of electronic health record sex and gender demographic fields: a metadata and mixed methods analysis

OBJECTIVES

Despite federally mandated collection of sex and gender demographics in the electronic health record (EHR), longitudinal assessments are lacking. We assessed sex and gender demographic field utilization using EHR metadata.

MATERIALS AND METHODS

Patients ≥18 years of age in the Mass General Brigham health system with a first Legal Sex entry (registration requirement) between January 8, 2018 and January 1, 2022 were included in this retrospective study. Metadata for all sex and gender fields (Legal Sex, Sex Assigned at Birth [SAAB], Gender Identity) were quantified by completion rates, user types, and longitudinal change. A nested qualitative study of providers from specialties with high and low field use identified themes related to utilization.

RESULTS

1 576 120 patients met inclusion criteria: 100% had a Legal Sex, 20% a Gender Identity, and 19% a SAAB; 321 185 patients had field changes other than initial Legal Sex entry. About 2% of patients had a subsequent Legal Sex change, and 25% of those had ≥2 changes; 20% of patients had ≥1 update to Gender Identity and 19% to SAAB. Excluding the first Legal Sex entry, administrators made most changes (67%) across all fields, followed by patients (25%), providers (7.2%), and automated Health Level-7 (HL7) interface messages (0.7%). Provider utilization varied by subspecialty; themes related to systems barriers and personal perceptions were identified.

DISCUSSION

Sex and gender demographic fields are primarily used by administrators and raise concern about data accuracy; provider use is heterogenous and lacking. Provider awareness of field availability and variable workflows may impede use.

CONCLUSION

EHR metadata highlights areas for improvement of sex and gender field utilization.

Transgender Patients Report Lower Satisfaction with Care Received than Cisgender Patients Receiving Care in an Academic Medical Care System

Purpose: Transgender and gender diverse (TGD) patients experience challenges in health care settings, including stigma, lack of culturally competent providers, and suboptimal gender-affirming care. However, differences in patient satisfaction between TGD patients compared with cisgender patients have been inadequately studied. This study aimed to assess such differences in patient satisfaction with care received in a large academic medical care system in Boston, Massachusetts. Methods: Routine patient satisfaction surveys were fielded from January to December 2021 and were summarized. Logistic regression models compared low net promoter scores (NPS; ≤6) between gender identity groups (cisgender women, transmasculine and nonbinary/genderqueer people assigned female at birth [AFAB], transfeminine and nonbinary/genderqueer people assigned male at birth) relative to cisgender men, adjusting for age, race, ethnicity, education, inpatient/outpatient service delivery, and distance from medical center. Results: Of 94,810 patients, 246 (0.3%) were TGD and 94,549 (99.7%) were cisgender. The mean age was 58.3 years (standard deviation = 16.6). Of the total sample, 17.0% of patients were people of color, 6.6% were Hispanic/Latinx, 48.6% were college graduates, and 2.6% had received inpatient care. In general, patient satisfaction with health care received was lower for TGD patients than for cisgender patients (7.3% vs. 4.5% reporting low NPS; adjusted odds ratio [aOR] = 1.14; 95% confidence interval [CI] = 0.70-1.85). Transmasculine and nonbinary/genderqueer patients AFAB had elevated odds of low NPS compared with cisgender men (8.8% vs. 3.6%; aOR = 1.71; 95% CI = 1.02-2.89). Conclusion: Future research is warranted to better understand factors driving lower ratings among TGD patients. Health care quality improvement efforts are needed to address gender identity inequities in care.

Decreased Anogenital Gonorrhea and Chlamydia in Transgender and Gender Diverse Primary Care Patients Receiving Gender-Affirming Hormone Therapy

BACKGROUND

Transgender and gender diverse (TGD) adults in the U.S. experience health disparities, including in anogenital sexually transmitted infections (STI). Gender-affirming hormone therapy (GAHT) is known to be medically necessary and improve health. Few studies have assessed the effect of GAHT on STI diagnoses.

OBJECTIVE

To evaluate the effect of GAHT delivered in primary care as an intervention to improve STI outcomes for TGD adults.

DESIGN

LEGACY is a longitudinal, multisite cohort study of adult TGD primary care patients from two federally qualified community health centers in Boston, MA, and New York, NY.

PARTICIPANTS

Electronic health record data for eligible adult TGD patients contributed to the LEGACY research data warehouse (RDW). A total of 6330 LEGACY RDW patients were followed from 2016 to 2019, with 2555 patients providing STI testing data.

MAIN MEASURES

GAHT exposure was being prescribed hormones, and the clinical outcome was anogenital gonorrhea or chlamydia diagnoses. Log-Poisson generalized estimating equations assessed the effect of prescription GAHT on primary outcomes, adjusting for age, race, ethnicity, gender identity, poverty level, health insurance, clinical site, and cohort years.

KEY RESULTS

The median age was 28 years (IQR = 13); the racial breakdown was 20.4% Black, 8.1% Multiracial, 6.9% Asian/Pacific Islander, 1.8% Other; 62.8% White; 21.3% Hispanic/Latinx; 47.0% were assigned female at birth, and 16.0% identified as nonbinary. 86.3% were prescribed hormones. Among those tested, the percentage of patients with a positive anogenital STI diagnosis ranged annually from 10.0 to 12.5% between 2016 and 2019. GAHT prescription was associated with a significant reduction in the risk of anogenital STI diagnosis (aRR = 0.75; 95% CI = 0.59-0.96) over follow-up.

CONCLUSIONS

GAHT delivered in primary care was associated with less STI morbidity in this TGD cohort over follow-up. Patients may benefit from individualized and tailored clinical care alongside GAHT to optimize STI outcomes.

Exploring gender euphoria in a sample of transgender and gender diverse patients at two U.S. urban community health centers

Transgender and gender diverse (TGD) people are affected by mental health inequities. Gender euphoria-positive emotions or joy in gender-may be associated with positive mental health. Between February 2019-July 2021, we surveyed 2,165 adult TGD patients (median age = 28 years; 29.2 % people of color; 29.6 % nonbinary; 81.0 % taking hormones) evaluating gender euphoria and mental health. Overall, 35.0 % self-reported gender euphoria, 50.9 % gender dysphoria, 23.5 % alcohol misuse, and 44.5 % resilience. Gender euphoria differed by race, gender, insurance, and hormone use, and was associated with reduced gender dysphoria (adjusted Odds Ratio[aOR] = 0.58; 95 % confidence interval [95 %CI] = 0.47-0.72) and alcohol misuse (aOR = 0.75; 95 %CI = 0.60-0.95), and increased resilience (aOR = 1.31; 95 %CI = 1.07-1.61). The construct of gender euphoria may be a promising mental health target.

'Wow, That's Me': Uneven Access To Gender-Affirming Care

A nonbinary/genderqueer person reflects on their experience pursuing a chest reduction as gender-affirming care.

Gender Affirmation-Related Information-Seeking Behaviors in a Diverse Sample of Transgender and Gender-Diverse Young Adults: Survey Study

BACKGROUND

Of the 1.6 million transgender and gender-diverse (TGD) people in the United States, approximately 700,000 are youth aged 13-24 years. Many factors make it difficult for TGD young people to identify resources for support and information related to gender identity and medical transition. These range from lack of knowledge to concerns about personal safety in the setting of increased antitransgender violence and legislative limitations on transgender rights. Web-based resources may be able to address some of the barriers to finding information and support, but youth may have difficulty finding relevant content or have concerns about the quality and content of information they find on the internet.

OBJECTIVE

We aim to understand ways TGD young adults look for web-based information about gender and health.

METHODS

In August 2022, 102 young adults completed a 1-time survey including closed- and open-ended responses. Individuals were recruited through the Prolific platform. Eligibility was restricted to people between the ages of 18-25 years who identified as transgender and were residents of the United States. The initial goal was to recruit 50 White individuals and 50 individuals who identified as Black, indigenous, or people of color. In total, 102 people were eventually enrolled.

RESULTS

Young adults reported looking on the internet for information about a broad range of topics related to both medical- and social-gender affirmation. Most participants preferred to obtain information via personal stories. Participants expressed a strong preference for obtaining information from other trans people.

CONCLUSIONS

There is a need for accessible, expert-informed information for TGD youth, particularly more information generated for the transgender community by members of the community.

Hepatitis C Virus Testing and Care Cascade Among Transgender and Gender Diverse Individuals

INTRODUCTION

Hepatitis C virus (HCV) prevalence among transgender and gender-diverse individuals ranges from 1.8% to 15.7% versus 1% in the general population. Previous HCV studies inclusive of transgender and gender-diverse individuals primarily rely on convenience-based sampling methods or are geographically restricted. The purpose of this study is to compare the prevalence of HCV diagnoses, testing, and care engagement between transgender and gender-diverse and cisgender individuals.

METHODS

Using Optum's de-identified Clinformatics® Data Mart Database, in 2022, the unadjusted prevalence of HCV testing among all adults and people who inject drugs from January 2001 to December 2019 was measured. Multivariable logistic regression was used to compare the adjusted odds of HCV diagnoses and care engagement by gender subgroup.

RESULTS

The overall unadjusted frequency of HCV diagnoses among transgender and gender-diverse individuals was approximately 3 times that of cisgender individuals (1.06% vs 0.38%, p<0.001), including among people who inject drugs (6.36% vs 2.36%, p=0.007). Compared with cisgender women, transfeminine/nonbinary individuals had over 5 times the adjusted odds of a HCV diagnosis and approximately 3.5 times the odds of being tested for HCV. In addition, compared with cisgender women, transfeminine/nonbinary individuals had significantly increased odds of having a HCV‒related procedure (e.g., abdominal ultrasounds, liver biopsies, Fibroscans). Cisgender men had significantly increased odds of receiving HCV medication compared with cisgender women.

CONCLUSIONS

Although testing was higher among transgender and gender-diverse individuals, the higher overall frequency of HCV diagnoses among transgender and gender-diverse than among cisgender individuals signals persistent health disparities. Interventions are warranted to prevent HCV and increase ongoing testing and treatment uptake among transgender and gender-diverse populations.

Digital-Assisted Self-interview of HIV or Sexually Transmitted Infection Risk Behaviors in Transmasculine Adults: Development and Field Testing of the Transmasculine Sexual Health Assessment

BACKGROUND

The sexual health of transmasculine (TM) people-those who identify as male, men, or nonbinary and were assigned a female sex at birth-is understudied. One barrier to conducting HIV- and sexually transmitted infection (STI)-related research with this population is how to best capture sexual risk data in an acceptable, gender-affirming, and accurate manner.

OBJECTIVE

This study aimed to report on the community-based process of developing, piloting, and refining a digitally deployed measure to assess self-reported sexual behaviors associated with HIV and STI transmission for research with TM adults.

METHODS

A multicomponent process was used to develop a digital-assisted self-interview to assess HIV and STI risk in TM people: gathering input from a Community Task Force; working with an interdisciplinary team of content experts in transgender medicine, epidemiology, and infectious diseases; conducting web-based focus groups; and iteratively refining the measure. We field-tested the measure with 141 TM people in the greater Boston, Massachusetts area to assess HIV and STI risk. Descriptive statistics characterized the distribution of sexual behaviors and HIV and STI transmission risk by the gender identity of sexual partners.

RESULTS

The Transmasculine Sexual Health Assessment (TM-SHA) measures the broad range of potential sexual behaviors TM people may engage in, including those which may confer risk for STIs and not just for HIV infection (ie, oral-genital contact); incorporates gender-affirming language (ie, genital or frontal vs vaginal); and asks sexual partnership characteristics (ie, partner gender). Among 141 individual participants (mean age 27, SD 5 years; range 21-29 years; n=21, 14.9% multiracial), 259 sexual partnerships and 15 sexual risk behaviors were reported. Participants engaged in a wide range of sexual behaviors, including fingering or fisting (receiving: n=170, 65.6%; performing: n=173, 66.8%), oral-genital sex (receiving: n=182, 70.3%; performing: n=216, 83.4%), anal-genital sex (receptive: n=31, 11.9%; insertive: n=9, 3.5%), frontal-genital sex (receptive: n=105, 40.5%; insertive: n=46, 17.8%), and sharing toys or prosthetics during insertive sex (n=62, 23.9%). Overall barrier use for each sexual behavior ranged from 10.9% (20/182) to 81% (25/31). Frontal receptive sex with genitals and no protective barrier was the highest (21/42, 50%) with cisgender male partners. In total, 14.9% (21/141) of participants reported a lifetime diagnosis of STI. The sexual history tool was highly acceptable to TM participants.

CONCLUSIONS

The TM-SHA is one of the first digital sexual health risk measures developed specifically with and exclusively for TM people. TM-SHA successfully integrates gender-affirming language and branching logic to capture a wide array of sexual behaviors. The measure elicits sexual behavior information needed to assess HIV and STI transmission risk behaviors. A strength of the tool is that detailed partner-by-partner data can be used to model partnership-level characteristics, not just individual-level participant data, to inform HIV and STI interventions.

Health and service utilization among a sample of gender-diverse youth of color: the TRUTH study

BACKGROUND

While there is growing research considering the experiences of transgender youth whose identities align with the gender binary, especially among young trans women, there are significantly fewer studies that accurately capture data about nonbinary youth, and even fewer studies capturing the experiences of transgender and gender diverse (TGD) youth of color. The purpose of this research was to assess the prevalence of sexual health behaviors, mental health challenges, substance use, and healthcare utilization among Black/African American, Latinx, Asian/Pacific Islander, indigenous and multi-racial/ethnic TGD youth, who have been largely underrepresented in research.

METHODS

A total of 108 TGD youth ages 16-24 were recruited into the Trans Youth of Color Study (TRUTH). Each participant completed a 90-min survey administered by a research assistant with more sensitive information collected using ACASI. In addition to a completing a survey administered by research staff, participants also participated in specimen collection, which included urine sampling to assess recent substance use without a prescription, self-collected rectal/frontal and throat swabs to test for gonorrhea and chlamydia, and a blood draw to test for recent use of drugs, gonorrhea and chlamydia, and syphilis. The sample was recruited at public venues, community outreach and referral, through social media outreach, and via participant referral. Cross-sectional analyses were from a single study visit.

RESULTS

Compared to rates among their cisgender peers, participants reported experiencing adverse social and structural determinants of health-e.g. food insecurity (61%), housing instability (30%), and limited access to healthcare (26% had no place to go for healthcare)-and elevated rates of illicit drug use (19-85%), mental health problems (e.g. 60% self-reported depression), and involvement in sexual risk-related behaviors (e.g. among those reporting penetrative sex 57-67% reported sex without a condom).

CONCLUSIONS

This study adds descriptions of both mental and sexual health outcomes of a non-clinical sample of TGD youth to the literature, particularly among young transgender men and gender nonbinary youth, who have frequently been excluded from previous studies of sexual health. The findings document experiences and behaviors among TGD youth that contribute to mental and sexual health concerns, including rates of substance use, and healthcare utilization.

Comparison of droplet spread in standard and laminar flow operating theatres: SPRAY study group

BACKGROUND

Reducing COVID-19 transmission relies on controlling droplet and aerosol spread. Fluorescein staining reveals microscopic droplets.

AIM

To compare the droplet spread in non-laminar and laminar air flow operating theatres.

METHODS

A 'cough-generator' was fixed to a theatre trolley at 45°. Fluorescein-stained 'secretions' were projected on to a series of calibrated targets. These were photographed under UV light and 'source detection' software measured droplet splatter size and distance.

FINDINGS

The smallest droplet detected was ∼120 μm and the largest ∼24,000 μm. An average of 25,862 spots was detected in the non-laminar theatre, compared with 11,430 in the laminar theatre (56% reduction). The laminar air flow mainly affected the smaller droplets (<1000 μm). The surface area covered with droplets was: 6% at 50 cm, 1% at 2 m, and 0.5% at 3 m in the non-laminar air flow; and 3%, 0.5%, and 0.2% in the laminar air flow, respectively.

CONCLUSION

Accurate mapping of droplet spread in clinical environments is possible using fluorescein staining and image analysis. The laminar air flow affected the smaller droplets but had limited effect on larger droplets in our 'aerosol-generating procedure' cough model. Our results indicate that the laminar air flow theatre requires similar post-surgery cleaning to the non-laminar, and staff should consider full personal protective equipment for medium- and high-risk patients.

Permissive and suppressive effects of dexamethasone on enzyme induction in hepatocyte co-cultures

1. Steroids are known to act as permissive factors in hepatocytes. This study shows that dexamethasone (DEX) is a permissive factor for induction of CYP2B1/2, CYP3A1, CYP2A1 and probably also CYP2C11 in cultures with primary rat hepatocytes. 2. The induction factor of phenobarbital (PB)-induced formation of 16beta-hydroxytestosterone (OHT), a testosterone biotransformation product predominantly formed by CYP2B1, is increased 18-fold by the addition of 32 nM DEX to the culture medium. Interestingly, higher concentrations of DEX up to 1000 nM led to a concentration-dependent maximally 5-fold decrease (p = 0.002) of phenobarbital-induced 16beta-OHT formation compared with the effect observed with 32 nM DEX. Thus, DEX shows permissive and suppressive effects on enzyme induction depending on the concentration of the glucocorticoid. 3. Qualitatively similar but smaller permissive and suppressive effects of DEX were observed for PB-induced CYP3A1 activity as evidenced by formation of 2beta-, 6beta- and 15beta-OHT. 4. DEX is a permissive factor for induction of CYP2A1 activity by 3-methylcholanthrene (3MC), as evidenced by the formation of 7alpha-OHT. Without addition of DEX, 3MC did not induce formation of 7alpha-OHT, whereas an almost 3-fold induction occurred in the presence of DEX. In contrast to CYP2B and CYP3A, concentrations up to 1000 nM DEX were not suppressive for the induction of CYP2A1. 5. We described recently a technique that allows preparation of cultures from cryopreserved hepatocytes. An almost identical influence of dexamethasone on enzyme induction was observed here in cultures from cryopreserved compared with freshly isolated hepatocytes. 6. Cultures with primary hepatocyte cultures represent a well-established technique for the study of drug-drug interactions. However, a large interlaboratory variation is known. Our study provides evidence that differences in glucocorticoid concentration in the culture medium contribute to this variation.

Gene expression profiling in skeletal muscle of Zucker diabetic fatty rats: implications for a role of stearoyl-CoA desaturase 1 in insulin resistance

AIMS/HYPOTHESIS

Insulin resistance in skeletal muscle is a hallmark of type 2 diabetes. Therefore, we sought to identify and validate genes involved in the development of insulin resistance in skeletal muscle.

MATERIALS

Differentially regulated genes in skeletal muscle of male obese insulin-resistant, and lean insulin-sensitive Zucker diabetic fatty (ZDF) rats were determined using Affymetrix microarrays. Based on these data, various aspects of glucose disposal, insulin signalling and fatty acid composition were analysed in a muscle cell line overexpressing stearoyl-CoA desaturase 1 (SCD1).

RESULTS

Gene expression profiling in insulin-resistant skeletal muscle revealed the most pronounced changes in gene expression for genes involved in lipid metabolism. Among these, Scd1 showed increased expression in insulin-resistant animals, correlating with increased amounts of palmitoleoyl-CoA. This was further investigated in a muscle cell line that overexpressed SCD1 and accumulated lipids, revealing impairments of glucose uptake and of different steps of the insulin signalling cascade. We also observed differential effects of high-glucose and fatty acid treatment on glucose uptake and long-chain fatty acyl-CoA profiles, and in particular an accumulation of palmitoleoyl-CoA in cells overexpressing SCD1.

CONCLUSIONS/INTERPRETATION

Insulin-resistant skeletal muscle of ZDF rats is characterised by a specific gene expression profile with increased levels of Scd1. An insulin-resistant phenotype similar to that obtained by treatment with palmitate and high glucose can be induced in vitro by overexpression of SCD1 in muscle cells. This supports the hypothesis that elevated SCD1 expression is a possible cause of insulin resistance and type 2 diabetes.

Duplicate marker loci can result in incorrect locus orders on linkage maps

Genetic linkage maps, constructed from multi-locus recombination data, are the basis for many applications of molecular markers. For the successful employment of a linkage map, it is essential that the linear order of loci on a chromosome is correct. The objectives of this theoretical study were to (1) investigate the occurrence of incorrect locus orders caused by duplicate marker loci, (2) develop a statistical test for the detection of duplicate markers, and (3) discuss the implications for practical applications of linkage maps. We derived conditions, under which incorrect locus orders do or do not occur with duplicate marker loci for the general case of n markers on a chromosome in a BC(1) mapping population. We further illustrated these conditions numerically for the special case of four markers. On the basis of the extent of segregation distortion, an exact test for the presence of duplicate marker loci was suggested and its power was investigated numerically. Incorrect locus orders caused by duplicate marker loci can (1) negatively affect the assignment of target genes to chromosome regions in a map-based cloning experiment, (2) hinder indirect selection for a favorable allele at a quantitative trait locus, and (3) decrease the efficiency of reducing the length of the chromosome segment attached to a target gene in marker-assisted backcrossing.

Identification of genetically linked RGAs by BAC screening in maize and implications for gene cloning, mapping and MAS

The resistance gene analogue (RGA) pic19 in maize, a candidate for sugarcane mosaic virus (SCMV) resistance gene (R gene) Scmv1, was used to screen a maize BAC library to identify homologous sequences in the maize genome and to investigate their genomic organisation. Fifteen positive BAC clones were identified and could be classified into five physically independent contigs consisting of overlapping clones. Genetic mapping clustered three contigs into the same genomic region as Scmv1 on chromosome 6S. The two remaining contigs mapped to the same region as a QTL for SCMV resistance on chromosome 1. Thus, RGAs mapping to a target region can be successfully used to identify further-linked candidate sequences. The pic19 homologous sequences of these clones revealed a sequence similarity of 94-98% on the nucleotide level. The high sequence similarity reveals potential problems for the use of RGAs as molecular markers. Their application in marker-assisted selection (MAS) and the construction of high-density genetic maps is complicated by the existence of closely linked homologues resulting in 'ghost' marker loci analogous to 'ghost' QTLs. Therefore, implementation of genomic library screening, including genetic mapping of potential homologues, seems necessary for the safe application of RGA markers in MAS and gene isolation.

Saturation of two chromosome regions conferring resistance to SCMV with SSR and AFLP markers by targeted BSA

Quantitative trait loci (QTLs) and bulked segregant analyses (BSA) identified the major genes Scmv1 on chromosome 6 and Scmv2 on chromosome 3, conferring resistance against sugarcane mosaic virus (SCMV) in maize. Both chromosome regions were further enriched for SSR and AFLP markers by targeted bulked segregant analysis (tBSA) in order to identify and map only markers closely linked to either Scmv1 or Scmv2. For identification of markers closely linked to the target genes, symptomless individuals of advanced backcross generations BC5 to BC9 were employed. All AFLP markers, identified by tBSA using 400 EcoRI/ MseI primer combinations, mapped within both targeted marker intervals. Fourteen SSR and six AFLP markers mapped to the Scmv1 region. Eleven SSR and 18 AFLP markers were located in the Scmv2 region. Whereas the linear order of SSR markers and the window size for the Scmv2 region fitted well with publicly available genetic maps, map distances and window size differed substantially for the Scmv1 region on chromosome 6. A possible explanation for the observed discrepancies is the presence of two closely linked resistance genes in the Scmv1 region.

Conversion of AFLP fragments tightly linked to SCMV resistance genes Scmv1 and Scmv2 into simple PCR-based markers

In a previous study, bulked segregant analysis with amplified fragment length polymorphisms (AFLPs) identified several markers closely linked to the sugarcane mosaic virus resistance genes Scmv1 on chromosome 6 and Scmv2 on chromosome 3. Six AFLP markers (E33M61-2, E33M52, E38M51, E82M57, E84M59 and E93M53) were located on chromosome 3 and two markers (E33M61-1 and E35M62-1) on chromosome 6. Our objective in the present study was to sequence the respective AFLP bands in order to convert these dominant markers into more simple and reliable polymerase chain reaction (PCR)-based sequence-tagged site markers. Six AFLP markers resulted either in complete identical sequences between the six inbreds investigated in this study or revealed single nucleotide polymorphisms within the inbred lines and were, therefore, not converted. One dominant AFLP marker (E35M62-1) was converted into an insertion/deletion (indel) marker and a second AFLP marker (E33M61-2) into a cleaved amplified polymorphic sequence marker. Mapping of both converted PCR-based markers confirmed their localization to the same chromosome region (E33M61-2 on chromosome 3; E35M62-1 on chromosome 6) as the original AFLP markers. Thus, these markers will be useful for marker-assisted selection and facilitate map-based cloning of SCMV resistance genes.

Development of RGA-CAPS markers and genetic mapping of candidate genes for sugarcane mosaic virus resistance in maize

Three previously published resistance gene analogues (RGAs), pic13, pic21 and pic19, were mapped in relation to sugarcane mosaic virus (SCMV) resistance genes ( Scmv1, Scmv2) in maize. We cloned these RGAs from six inbreds including three SCMV-resistant lines (D21, D32, FAP1360A) and three SCMV-susceptible lines (D145, D408, F7). Pairwise sequence alignments among the six inbreds revealed a frequency of one single nucleotide polymorphism (SNP) per 33 bp for the three RGAs, indicating a high degree of polymorphism and a high probability of success in converting RGAs into codominant cleaved amplified polymorphic sequence (CAPS) markers compared to other sequences. SNPs were used to develop CAPS markers for mapping of the three RGAs in relation to Scmv1 (chromosome 6) and Scmv2 (chromosome 3), and for pedigree analyses of resistant inbred lines. By genetic mapping pic21 was shown to be different from Scmv2, whereas pic19 and pic13 are still candidates for Scmv1 and Scmv2, respectively, due to genetic mapping and consistent restriction patterns of ancestral lines.